21162420 has 72 divisors (see below), whose sum is σ = 64963080. Its totient is φ = 5575680.

The previous prime is 21162403. The next prime is 21162439. The reversal of 21162420 is 2426112.

21162420 is a `hidden beast` number, since 21 + 1 + 624 + 20 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 3370896 + 17791524 = 1836^2 + 4218^2 .

It is a super-3 number, since 3×21162420³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21162393 and 21162402.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15360 + ... + 16680.

It is an arithmetic number, because the mean of its divisors is an integer number (902265).

Almost surely, 2^21162420 is an apocalyptic number.

21162420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21162420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32481540).

21162420 is an abundant number, since it is smaller than the sum of its proper divisors (43800660).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21162420 is a wasteful number, since it uses less digits than its factorization.

21162420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1425 (or 1420 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21162420 is about 4600.2630359578. The cubic root of 21162420 is about 276.6018686655.

Adding to 21162420 its reverse (2426112), we get a palindrome (23588532).

The spelling of 21162420 in words is "twenty-one million, one hundred sixty-two thousand, four hundred twenty".