21521345472 has 84 divisors (see below), whose sum is σ = 67294984536. Its totient is φ = 6521617920.

The previous prime is 21521345471. The next prime is 21521345491. The reversal of 21521345472 is 27454312512.

21521345472 is a `hidden beast` number, since 2 + 1 + 52 + 134 + 5 + 472 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521345471) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1692003 + ... + 1704674.

Almost surely, 2^21521345472 is an apocalyptic number.

21521345472 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21521345472 is an abundant number, since it is smaller than the sum of its proper divisors (45773639064).

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

21521345472 is a wasteful number, since it uses less digits than its factorization.

21521345472 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3396706 (or 3396693 counting only the distinct ones).

The product of its digits is 67200, while the sum is 36.

Adding to 21521345472 its reverse (27454312512), we get a palindrome (48975657984).

The spelling of 21521345472 in words is "twenty-one billion, five hundred twenty-one million, three hundred forty-five thousand, four hundred seventy-two".