21538902 has 64 divisors (see below), whose sum is σ = 56070144. Its totient is φ = 5348640.

The previous prime is 21538897. The next prime is 21538903. The reversal of 21538902 is 20983512.

It is a happy number.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21538902.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538903) 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, 9613 + ... + 11639.

It is an arithmetic number, because the mean of its divisors is an integer number (876096).

Almost surely, 2^21538902 is an apocalyptic number.

21538902 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21538902, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28035072).

21538902 is an abundant number, since it is smaller than the sum of its proper divisors (34531242).

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

21538902 is a wasteful number, since it uses less digits than its factorization.

21538902 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2073.

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 21538902 is about 4641.0022624429. The cubic root of 21538902 is about 278.2324970484.

The spelling of 21538902 in words is "twenty-one million, five hundred thirty-eight thousand, nine hundred two".