21105513521 has 8 divisors (see below), whose sum is σ = 21386937600. Its totient is φ = 20824446240.

The previous prime is 21105513511. The next prime is 21105513577. The reversal of 21105513521 is 12531550112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21105513521 is a prime.

It is a super-2 number, since 2×21105513521² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21105513511) 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, 30965 + ... + 207773.

It is an arithmetic number, because the mean of its divisors is an integer number (2673367200).

Almost surely, 2^21105513521 is an apocalyptic number.

It is an amenable number.

21105513521 is a deficient number, since it is larger than the sum of its proper divisors (281424079).

21105513521 is a wasteful number, since it uses less digits than its factorization.

21105513521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178399.

The product of its (nonzero) digits is 1500, while the sum is 26.

The spelling of 21105513521 in words is "twenty-one billion, one hundred five million, five hundred thirteen thousand, five hundred twenty-one".