20567537581 has 2 divisors, whose sum is σ = 20567537582. Its totient is φ = 20567537580.

The previous prime is 20567537489. The next prime is 20567537597. The reversal of 20567537581 is 18573576502.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14659155625 + 5908381956 = 121075^2 + 76866^2 .

It is a cyclic number.

It is not a de Polignac number, because 20567537581 - 2³¹ = 18420053933 is a prime.

It is a super-2 number, since 2×20567537581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20567637581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10283768790 + 10283768791.

It is an arithmetic number, because the mean of its divisors is an integer number (10283768791).

Almost surely, 2^20567537581 is an apocalyptic number.

It is an amenable number.

20567537581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20567537581 is an equidigital number, since it uses as much as digits as its factorization.

20567537581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1764000, while the sum is 49.

The spelling of 20567537581 in words is "twenty billion, five hundred sixty-seven million, five hundred thirty-seven thousand, five hundred eighty-one".