20640321861 has 4 divisors (see below), whose sum is σ = 27520429152. Its totient is φ = 13760214572.

The previous prime is 20640321833. The next prime is 20640321893. The reversal of 20640321861 is 16812304602.

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 20640321861 - 2⁵ = 20640321829 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640321461) 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, 3440053641 + ... + 3440053646.

It is an arithmetic number, because the mean of its divisors is an integer number (6880107288).

Almost surely, 2^20640321861 is an apocalyptic number.

It is an amenable number.

20640321861 is a deficient number, since it is larger than the sum of its proper divisors (6880107291).

20640321861 is an equidigital number, since it uses as much as digits as its factorization.

20640321861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6880107290.

The product of its (nonzero) digits is 13824, while the sum is 33.

The spelling of 20640321861 in words is "twenty billion, six hundred forty million, three hundred twenty-one thousand, eight hundred sixty-one".