20639343657 has 4 divisors (see below), whose sum is σ = 27519124880. Its totient is φ = 13759562436.

The previous prime is 20639343583. The next prime is 20639343677. The reversal of 20639343657 is 75634393602.

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 not a de Polignac number, because 20639343657 - 2¹¹ = 20639341609 is a prime.

It is a super-2 number, since 2×20639343657² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20639343677) 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, 3439890607 + ... + 3439890612.

It is an arithmetic number, because the mean of its divisors is an integer number (6879781220).

Almost surely, 2^20639343657 is an apocalyptic number.

It is an amenable number.

20639343657 is a deficient number, since it is larger than the sum of its proper divisors (6879781223).

20639343657 is an equidigital number, since it uses as much as digits as its factorization.

20639343657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6879781222.

The product of its (nonzero) digits is 2449440, while the sum is 48.

The spelling of 20639343657 in words is "twenty billion, six hundred thirty-nine million, three hundred forty-three thousand, six hundred fifty-seven".