661501931 has 2 divisors, whose sum is σ = 661501932. Its totient is φ = 661501930.

The previous prime is 661501871. The next prime is 661501987. The reversal of 661501931 is 139105166.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661501931 - 2¹⁴ = 661485547 is a prime.

It is a super-2 number, since 2×661501931² = 875169609433457522, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661501031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330750965 + 330750966.

It is an arithmetic number, because the mean of its divisors is an integer number (330750966).

Almost surely, 2^661501931 is an apocalyptic number.

661501931 is a deficient number, since it is larger than the sum of its proper divisors (1).

661501931 is an equidigital number, since it uses as much as digits as its factorization.

661501931 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4860, while the sum is 32.

The square root of 661501931 is about 25719.6798385983. The cubic root of 661501931 is about 871.3187078618.

The spelling of 661501931 in words is "six hundred sixty-one million, five hundred one thousand, nine hundred thirty-one".