20971537581 has 16 divisors (see below), whose sum is σ = 28726632000. Its totient is φ = 13598967168.

The previous prime is 20971537571. The next prime is 20971537591. The reversal of 20971537581 is 18573517902.

It is an interprime number because it is at equal distance from previous prime (20971537571) and next prime (20971537591).

It is not a de Polignac number, because 20971537581 - 2⁵ = 20971537549 is a prime.

It is a super-2 number, since 2×20971537581² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20971537581.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20971537571) 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, 355450 + ... + 410228.

It is an arithmetic number, because the mean of its divisors is an integer number (1795414500).

Almost surely, 2^20971537581 is an apocalyptic number.

It is an amenable number.

20971537581 is a deficient number, since it is larger than the sum of its proper divisors (7755094419).

20971537581 is a wasteful number, since it uses less digits than its factorization.

20971537581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58268.

The product of its (nonzero) digits is 529200, while the sum is 48.

The spelling of 20971537581 in words is "twenty billion, nine hundred seventy-one million, five hundred thirty-seven thousand, five hundred eighty-one".