688926409 has 2 divisors, whose sum is σ = 688926410. Its totient is φ = 688926408.

The previous prime is 688926379. The next prime is 688926443. The reversal of 688926409 is 904629886.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 397882809 + 291043600 = 19947^2 + 17060^2 .

It is a cyclic number.

It is not a de Polignac number, because 688926409 - 2¹⁵ = 688893641 is a prime.

It is not a weakly prime, because it can be changed into another prime (688926209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344463204 + 344463205.

It is an arithmetic number, because the mean of its divisors is an integer number (344463205).

Almost surely, 2^688926409 is an apocalyptic number.

It is an amenable number.

688926409 is a deficient number, since it is larger than the sum of its proper divisors (1).

688926409 is an equidigital number, since it uses as much as digits as its factorization.

688926409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1492992, while the sum is 52.

The square root of 688926409 is about 26247.4076624721. The cubic root of 688926409 is about 883.1970525566.

The spelling of 688926409 in words is "six hundred eighty-eight million, nine hundred twenty-six thousand, four hundred nine".