21153420 has 96 divisors (see below), whose sum is σ = 67415040. Its totient is φ = 5503680.

The previous prime is 21153409. The next prime is 21153427. The reversal of 21153420 is 2435112.

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 = 21153393 and 21153402.

It is not an unprimeable number, because it can be changed into a prime (21153427) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22765 + ... + 23675.

It is an arithmetic number, because the mean of its divisors is an integer number (702240).

Almost surely, 2^21153420 is an apocalyptic number.

21153420 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 21153420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33707520).

21153420 is an abundant number, since it is smaller than the sum of its proper divisors (46261620).

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

21153420 is a wasteful number, since it uses less digits than its factorization.

21153420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 972 (or 964 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21153420 is about 4599.2847269983. The cubic root of 21153420 is about 276.5626518241.

Adding to 21153420 its reverse (2435112), we get a palindrome (23588532).

The spelling of 21153420 in words is "twenty-one million, one hundred fifty-three thousand, four hundred twenty".