642688987 has 2 divisors, whose sum is σ = 642688988. Its totient is φ = 642688986.

The previous prime is 642688967. The next prime is 642689009. The reversal of 642688987 is 789886246.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-642688987 is a prime.

It is a super-2 number, since 2×642688987² = 826098268022172338, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (642688967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321344493 + 321344494.

It is an arithmetic number, because the mean of its divisors is an integer number (321344494).

Almost surely, 2^642688987 is an apocalyptic number.

642688987 is a deficient number, since it is larger than the sum of its proper divisors (1).

642688987 is an equidigital number, since it uses as much as digits as its factorization.

642688987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9289728, while the sum is 58.

The square root of 642688987 is about 25351.3113467529. The cubic root of 642688987 is about 862.9791160619.

The spelling of 642688987 in words is "six hundred forty-two million, six hundred eighty-eight thousand, nine hundred eighty-seven".