21311504021 has 16 divisors (see below), whose sum is σ = 22601905200. Its totient is φ = 20058931200.

The previous prime is 21311504009. The next prime is 21311504023. The reversal of 21311504021 is 12040511312.

It can be written as a sum of positive squares in 8 ways, for example, as 3104049796 + 18207454225 = 55714^2 + 134935^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311504021 - 2¹⁸ = 21311241877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311503984 and 21311504002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311504023) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1668941 + ... + 1681661.

It is an arithmetic number, because the mean of its divisors is an integer number (1412619075).

Almost surely, 2^21311504021 is an apocalyptic number.

It is an amenable number.

21311504021 is a deficient number, since it is larger than the sum of its proper divisors (1290401179).

21311504021 is a wasteful number, since it uses less digits than its factorization.

21311504021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14200.

The product of its (nonzero) digits is 240, while the sum is 20.

The spelling of 21311504021 in words is "twenty-one billion, three hundred eleven million, five hundred four thousand, twenty-one".