688021937 has 2 divisors, whose sum is σ = 688021938. Its totient is φ = 688021936.

The previous prime is 688021933. The next prime is 688021949. The reversal of 688021937 is 739120886.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 687698176 + 323761 = 26224^2 + 569^2 .

It is a cyclic number.

It is not a de Polignac number, because 688021937 - 2² = 688021933 is a prime.

It is not a weakly prime, because it can be changed into another prime (688021933) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344010968 + 344010969.

It is an arithmetic number, because the mean of its divisors is an integer number (344010969).

Almost surely, 2^688021937 is an apocalyptic number.

It is an amenable number.

688021937 is a deficient number, since it is larger than the sum of its proper divisors (1).

688021937 is an equidigital number, since it uses as much as digits as its factorization.

688021937 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 145152, while the sum is 44.

The square root of 688021937 is about 26230.1722640169. The cubic root of 688021937 is about 882.8103751432.

The spelling of 688021937 in words is "six hundred eighty-eight million, twenty-one thousand, nine hundred thirty-seven".