21621456 has 60 divisors (see below), whose sum is σ = 61673508. Its totient is φ = 7068672.

The previous prime is 21621437. The next prime is 21621463. The reversal of 21621456 is 65412612.

It can be written as a sum of positive squares in 2 ways, for example, as 12110400 + 9511056 = 3480^2 + 3084^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6216 + ... + 9048.

Almost surely, 2^21621456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21621456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30836754).

21621456 is an abundant number, since it is smaller than the sum of its proper divisors (40052052).

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

21621456 is a wasteful number, since it uses less digits than its factorization.

21621456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2900 (or 2891 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21621456 is about 4649.8877405804. The cubic root of 21621456 is about 278.5875123991.

The spelling of 21621456 in words is "twenty-one million, six hundred twenty-one thousand, four hundred fifty-six".