21215521506 has 16 divisors (see below), whose sum is σ = 42665470848. Its totient is φ = 7032769200.

The previous prime is 21215521499. The next prime is 21215521529. The reversal of 21215521506 is 60512551212.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9766650 + ... + 9768821.

It is an arithmetic number, because the mean of its divisors is an integer number (2666591928).

Almost surely, 2^21215521506 is an apocalyptic number.

21215521506 is an abundant number, since it is smaller than the sum of its proper divisors (21449949342).

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

21215521506 is a wasteful number, since it uses less digits than its factorization.

21215521506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19535657.

The product of its (nonzero) digits is 6000, while the sum is 30.

The spelling of 21215521506 in words is "twenty-one billion, two hundred fifteen million, five hundred twenty-one thousand, five hundred six".