31665513661 has 4 divisors (see below), whose sum is σ = 31666314400. Its totient is φ = 31664712924.

The previous prime is 31665513643. The next prime is 31665513707. The reversal of 31665513661 is 16631556613.

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 31665513661 - 2²³ = 31657125053 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31665513161) 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, 337791 + ... + 421228.

It is an arithmetic number, because the mean of its divisors is an integer number (7916578600).

Almost surely, 2^31665513661 is an apocalyptic number.

It is an amenable number.

31665513661 is a deficient number, since it is larger than the sum of its proper divisors (800739).

31665513661 is an equidigital number, since it uses as much as digits as its factorization.

31665513661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 800738.

The product of its digits is 291600, while the sum is 43.

The spelling of 31665513661 in words is "thirty-one billion, six hundred sixty-five million, five hundred thirteen thousand, six hundred sixty-one".