661899985127 has 2 divisors, whose sum is σ = 661899985128. Its totient is φ = 661899985126.

The previous prime is 661899985081. The next prime is 661899985141. The reversal of 661899985127 is 721589998166.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 661899985127 - 2¹⁸ = 661899722983 is a prime.

It is a super-2 number, since 2×661899985127² (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 (661899985177) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330949992563 + 330949992564.

It is an arithmetic number, because the mean of its divisors is an integer number (330949992564).

Almost surely, 2^661899985127 is an apocalyptic number.

661899985127 is a deficient number, since it is larger than the sum of its proper divisors (1).

661899985127 is an equidigital number, since it uses as much as digits as its factorization.

661899985127 is an evil number, because the sum of its binary digits is even.

The product of its digits is 117573120, while the sum is 71.

The spelling of 661899985127 in words is "six hundred sixty-one billion, eight hundred ninety-nine million, nine hundred eighty-five thousand, one hundred twenty-seven".