688417821 has 48 divisors (see below), whose sum is σ = 1226848896. Its totient is φ = 362233728.

The previous prime is 688417817. The next prime is 688417859. The reversal of 688417821 is 128714886.

It is not a de Polignac number, because 688417821 - 2² = 688417817 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688417801) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 460351 + ... + 461843.

It is an arithmetic number, because the mean of its divisors is an integer number (25559352).

Almost surely, 2^688417821 is an apocalyptic number.

It is an amenable number.

688417821 is a deficient number, since it is larger than the sum of its proper divisors (538431075).

688417821 is a wasteful number, since it uses less digits than its factorization.

688417821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2082 (or 2079 counting only the distinct ones).

The product of its digits is 172032, while the sum is 45.

The square root of 688417821 is about 26237.7175264923. The cubic root of 688417821 is about 882.9796640731.

The spelling of 688417821 in words is "six hundred eighty-eight million, four hundred seventeen thousand, eight hundred twenty-one".