688903981 has 4 divisors (see below), whose sum is σ = 718856352. Its totient is φ = 658951612.

The previous prime is 688903973. The next prime is 688903987. The reversal of 688903981 is 189309886.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 688903981 - 2³ = 688903973 is a prime.

It is a super-2 number, since 2×688903981² = 949177390075296722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688903987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14976151 + ... + 14976196.

It is an arithmetic number, because the mean of its divisors is an integer number (179714088).

Almost surely, 2^688903981 is an apocalyptic number.

It is an amenable number.

688903981 is a deficient number, since it is larger than the sum of its proper divisors (29952371).

688903981 is a wasteful number, since it uses less digits than its factorization.

688903981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29952370.

The product of its (nonzero) digits is 746496, while the sum is 52.

The square root of 688903981 is about 26246.9804168022. The cubic root of 688903981 is about 883.1874682923.

The spelling of 688903981 in words is "six hundred eighty-eight million, nine hundred three thousand, nine hundred eighty-one".