21450420 has 60 divisors (see below), whose sum is σ = 67295844. Its totient is φ = 5719680.

The previous prime is 21450389. The next prime is 21450431. The reversal of 21450420 is 2405412.

It can be written as a sum of positive squares in 2 ways, for example, as 16548624 + 4901796 = 4068^2 + 2214^2 .

It is a tau number, because it is divible by the number of its divisors (60).

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 = 21450393 and 21450402.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 5001 + ... + 8240.

Almost surely, 2^21450420 is an apocalyptic number.

21450420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21450420 is an abundant number, since it is smaller than the sum of its proper divisors (45845424).

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

21450420 is a wasteful number, since it uses less digits than its factorization.

21450420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13262 (or 13251 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21450420 is about 4631.4598130611. The cubic root of 21450420 is about 277.8509802925.

Adding to 21450420 its reverse (2405412), we get a palindrome (23855832).

The spelling of 21450420 in words is "twenty-one million, four hundred fifty thousand, four hundred twenty".