21015521456 has 20 divisors (see below), whose sum is σ = 40721345304. Its totient is φ = 10506787200.

The previous prime is 21015521453. The next prime is 21015521503. The reversal of 21015521456 is 65412551012.

It is not an unprimeable number, because it can be changed into a prime (21015521453) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136676 + ... + 246396.

Almost surely, 2^21015521456 is an apocalyptic number.

It is an amenable number.

21015521456 is a deficient number, since it is larger than the sum of its proper divisors (19705823848).

21015521456 is a wasteful number, since it uses less digits than its factorization.

21015521456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121700 (or 121694 counting only the distinct ones).

The product of its (nonzero) digits is 12000, while the sum is 32.

The spelling of 21015521456 in words is "twenty-one billion, fifteen million, five hundred twenty-one thousand, four hundred fifty-six".