688657421 has 8 divisors (see below), whose sum is σ = 723179904. Its totient is φ = 654516720.

The previous prime is 688657393. The next prime is 688657429. The reversal of 688657421 is 124756886.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688657421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688657429) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 91745 + ... + 98966.

It is an arithmetic number, because the mean of its divisors is an integer number (90397488).

Almost surely, 2^688657421 is an apocalyptic number.

It is an amenable number.

688657421 is a deficient number, since it is larger than the sum of its proper divisors (34522483).

688657421 is a wasteful number, since it uses less digits than its factorization.

688657421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 190891.

The product of its digits is 645120, while the sum is 47.

The square root of 688657421 is about 26242.2830752204. The cubic root of 688657421 is about 883.0820909140.

The spelling of 688657421 in words is "six hundred eighty-eight million, six hundred fifty-seven thousand, four hundred twenty-one".