687631979 has 2 divisors, whose sum is σ = 687631980. Its totient is φ = 687631978.

The previous prime is 687631957. The next prime is 687631981. The reversal of 687631979 is 979136786.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 687631979 - 2⁸ = 687631723 is a prime.

Together with 687631981, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (687631999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343815989 + 343815990.

It is an arithmetic number, because the mean of its divisors is an integer number (343815990).

Almost surely, 2^687631979 is an apocalyptic number.

687631979 is a deficient number, since it is larger than the sum of its proper divisors (1).

687631979 is an equidigital number, since it uses as much as digits as its factorization.

687631979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3429216, while the sum is 56.

The square root of 687631979 is about 26222.7378242624. The cubic root of 687631979 is about 882.6435568050.

The spelling of 687631979 in words is "six hundred eighty-seven million, six hundred thirty-one thousand, nine hundred seventy-nine".