21521521551 has 8 divisors (see below), whose sum is σ = 28711682560. Its totient is φ = 14339520792.

The previous prime is 21521521523. The next prime is 21521521577. The reversal of 21521521551 is 15512512512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21521521551 - 2⁷ = 21521521423 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521525551) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2033905 + ... + 2044458.

It is an arithmetic number, because the mean of its divisors is an integer number (3588960320).

Almost surely, 2^21521521551 is an apocalyptic number.

21521521551 is a deficient number, since it is larger than the sum of its proper divisors (7190161009).

21521521551 is a wasteful number, since it uses less digits than its factorization.

21521521551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4080125.

The product of its digits is 5000, while the sum is 30.

The spelling of 21521521551 in words is "twenty-one billion, five hundred twenty-one million, five hundred twenty-one thousand, five hundred fifty-one".