21505338972 has 120 divisors (see below), whose sum is σ = 62497162112. Its totient is φ = 6403536000.

The previous prime is 21505338971. The next prime is 21505338973. The reversal of 21505338972 is 27983350512.

21505338972 is a `hidden beast` number, since 2 + 150 + 53 + 389 + 72 = 666.

It is an interprime number because it is at equal distance from previous prime (21505338971) and next prime (21505338973).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505338971) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 48222 + ... + 212922.

Almost surely, 2^21505338972 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 21505338972, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31248581056).

21505338972 is an abundant number, since it is smaller than the sum of its proper divisors (40991823140).

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

21505338972 is a wasteful number, since it uses less digits than its factorization.

21505338972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164761 (or 164750 counting only the distinct ones).

The product of its (nonzero) digits is 453600, while the sum is 45.

The spelling of 21505338972 in words is "twenty-one billion, five hundred five million, three hundred thirty-eight thousand, nine hundred seventy-two".