642631657 has 2 divisors, whose sum is σ = 642631658. Its totient is φ = 642631656.

The previous prime is 642631609. The next prime is 642631667. The reversal of 642631657 is 756136246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 612117081 + 30514576 = 24741^2 + 5524^2 .

It is a cyclic number.

It is not a de Polignac number, because 642631657 - 2¹⁹ = 642107369 is a prime.

It is not a weakly prime, because it can be changed into another prime (642631607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321315828 + 321315829.

It is an arithmetic number, because the mean of its divisors is an integer number (321315829).

Almost surely, 2^642631657 is an apocalyptic number.

It is an amenable number.

642631657 is a deficient number, since it is larger than the sum of its proper divisors (1).

642631657 is an equidigital number, since it uses as much as digits as its factorization.

642631657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 181440, while the sum is 40.

The square root of 642631657 is about 25350.1806107964. The cubic root of 642631657 is about 862.9534550942.

It can be divided in two parts, 6426 and 31657, that added together give a palindrome (38083).

The spelling of 642631657 in words is "six hundred forty-two million, six hundred thirty-one thousand, six hundred fifty-seven".