21526720491 has 16 divisors (see below), whose sum is σ = 30224416640. Its totient is φ = 13590659520.

The previous prime is 21526720489. The next prime is 21526720493. The reversal of 21526720491 is 19402762512.

It is an interprime number because it is at equal distance from previous prime (21526720489) and next prime (21526720493).

It is not a de Polignac number, because 21526720491 - 2¹ = 21526720489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21526720493) 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, 82551 + ... + 223311.

It is an arithmetic number, because the mean of its divisors is an integer number (1889026040).

Almost surely, 2^21526720491 is an apocalyptic number.

21526720491 is a deficient number, since it is larger than the sum of its proper divisors (8697696149).

21526720491 is a wasteful number, since it uses less digits than its factorization.

21526720491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143466.

The product of its (nonzero) digits is 60480, while the sum is 39.

The spelling of 21526720491 in words is "twenty-one billion, five hundred twenty-six million, seven hundred twenty thousand, four hundred ninety-one".