21000972544 has 18 divisors (see below), whose sum is σ = 41919910550. Its totient is φ = 10500486144.

The previous prime is 21000972529. The next prime is 21000972547. The reversal of 21000972544 is 44527900012.

It can be written as a sum of positive squares in only one way, i.e., 14954354944 + 6046617600 = 122288^2 + 77760^2 .

It is not an unprimeable number, because it can be changed into a prime (21000972547) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41017269 + ... + 41017780.

Almost surely, 2^21000972544 is an apocalyptic number.

It is an amenable number.

21000972544 is a deficient number, since it is larger than the sum of its proper divisors (20918938006).

21000972544 is an frugal number, since it uses more digits than its factorization.

21000972544 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 82035065 (or 82035051 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 34.

The spelling of 21000972544 in words is "twenty-one billion, nine hundred seventy-two thousand, five hundred forty-four".