642186581 has 2 divisors, whose sum is σ = 642186582. Its totient is φ = 642186580.

The previous prime is 642186539. The next prime is 642186593. The reversal of 642186581 is 185681246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 410872900 + 231313681 = 20270^2 + 15209^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642186581 is a prime.

It is a super-2 number, since 2×642186581² = 824807209632939122, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642186481) 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, 321093290 + 321093291.

It is an arithmetic number, because the mean of its divisors is an integer number (321093291).

Almost surely, 2^642186581 is an apocalyptic number.

It is an amenable number.

642186581 is a deficient number, since it is larger than the sum of its proper divisors (1).

642186581 is an equidigital number, since it uses as much as digits as its factorization.

642186581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 92160, while the sum is 41.

The square root of 642186581 is about 25341.4005335143. The cubic root of 642186581 is about 862.7541866792.

The spelling of 642186581 in words is "six hundred forty-two million, one hundred eighty-six thousand, five hundred eighty-one".