2640637581 has 4 divisors (see below), whose sum is σ = 3520850112. Its totient is φ = 1760425052.

The previous prime is 2640637547. The next prime is 2640637589. The reversal of 2640637581 is 1857360462.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2640637581 - 2¹¹ = 2640635533 is a prime.

It is a super-2 number, since 2×2640637581² = 13945933668379063122, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2640637589) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 440106261 + ... + 440106266.

It is an arithmetic number, because the mean of its divisors is an integer number (880212528).

Almost surely, 2^2640637581 is an apocalyptic number.

It is an amenable number.

2640637581 is a deficient number, since it is larger than the sum of its proper divisors (880212531).

2640637581 is an equidigital number, since it uses as much as digits as its factorization.

2640637581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 880212530.

The product of its (nonzero) digits is 241920, while the sum is 42.

The square root of 2640637581 is about 51387.1343917911. The cubic root of 2640637581 is about 1382.1958985252.

The spelling of 2640637581 in words is "two billion, six hundred forty million, six hundred thirty-seven thousand, five hundred eighty-one".