21721634527 has 2 divisors, whose sum is σ = 21721634528. Its totient is φ = 21721634526.

The previous prime is 21721634507. The next prime is 21721634563. The reversal of 21721634527 is 72543612712.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21721634527 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21721634527.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21721634507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10860817263 + 10860817264.

It is an arithmetic number, because the mean of its divisors is an integer number (10860817264).

Almost surely, 2^21721634527 is an apocalyptic number.

21721634527 is a deficient number, since it is larger than the sum of its proper divisors (1).

21721634527 is an equidigital number, since it uses as much as digits as its factorization.

21721634527 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 40.

The spelling of 21721634527 in words is "twenty-one billion, seven hundred twenty-one million, six hundred thirty-four thousand, five hundred twenty-seven".