21255630 has 64 divisors (see below), whose sum is σ = 57044736. Its totient is φ = 5024000.

The previous prime is 21255613. The next prime is 21255653. The reversal of 21255630 is 3655212.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21255630.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12745 + ... + 14315.

It is an arithmetic number, because the mean of its divisors is an integer number (891324).

Almost surely, 2^21255630 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21255630, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28522368).

21255630 is an abundant number, since it is smaller than the sum of its proper divisors (35789106).

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

21255630 is a wasteful number, since it uses less digits than its factorization.

21255630 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1633.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21255630 is about 4610.3828474434. The cubic root of 21255630 is about 277.0073720707.

The spelling of 21255630 in words is "twenty-one million, two hundred fifty-five thousand, six hundred thirty".