688642531 has 2 divisors, whose sum is σ = 688642532. Its totient is φ = 688642530.

The previous prime is 688642529. The next prime is 688642547. The reversal of 688642531 is 135246886.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 688642531 - 2¹ = 688642529 is a prime.

It is a super-2 number, since 2×688642531² = 948457071004171922, which contains 22 as substring.

Together with 688642529, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (688642501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344321265 + 344321266.

It is an arithmetic number, because the mean of its divisors is an integer number (344321266).

Almost surely, 2^688642531 is an apocalyptic number.

688642531 is a deficient number, since it is larger than the sum of its proper divisors (1).

688642531 is an equidigital number, since it uses as much as digits as its factorization.

688642531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 276480, while the sum is 43.

The square root of 688642531 is about 26241.9993712369. Note that the first 3 decimals coincide. The cubic root of 688642531 is about 883.0757262656.

The spelling of 688642531 in words is "six hundred eighty-eight million, six hundred forty-two thousand, five hundred thirty-one".