661641564631 has 2 divisors, whose sum is σ = 661641564632. Its totient is φ = 661641564630.

The previous prime is 661641564601. The next prime is 661641564707. The reversal of 661641564631 is 136465146166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661641564631 - 2⁵ = 661641564599 is a prime.

It is a super-2 number, since 2×661641564631² (a number of 24 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661641564601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330820782315 + 330820782316.

It is an arithmetic number, because the mean of its divisors is an integer number (330820782316).

Almost surely, 2^661641564631 is an apocalyptic number.

661641564631 is a deficient number, since it is larger than the sum of its proper divisors (1).

661641564631 is an equidigital number, since it uses as much as digits as its factorization.

661641564631 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1866240, while the sum is 49.

The spelling of 661641564631 in words is "six hundred sixty-one billion, six hundred forty-one million, five hundred sixty-four thousand, six hundred thirty-one".