21615844971 has 32 divisors (see below), whose sum is σ = 33832770048. Its totient is φ = 12018159360.

The previous prime is 21615844949. The next prime is 21615845029. The reversal of 21615844971 is 17944851612.

It is not a de Polignac number, because 21615844971 - 2⁶ = 21615844907 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21615844971.

It is not an unprimeable number, because it can be changed into a prime (21615840971) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 287500 + ... + 354806.

It is an arithmetic number, because the mean of its divisors is an integer number (1057274064).

Almost surely, 2^21615844971 is an apocalyptic number.

21615844971 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21615844971 is a deficient number, since it is larger than the sum of its proper divisors (12216925077).

21615844971 is a wasteful number, since it uses less digits than its factorization.

21615844971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67731.

The product of its digits is 483840, while the sum is 48.

It can be divided in two parts, 21615 and 844971, that added together give a triangular number (866586 = T₁₃₁₆).

The spelling of 21615844971 in words is "twenty-one billion, six hundred fifteen million, eight hundred forty-four thousand, nine hundred seventy-one".