688645221 has 24 divisors (see below), whose sum is σ = 1030109472. Its totient is φ = 405540000.

The previous prime is 688645211. The next prime is 688645261. The reversal of 688645221 is 122546886.

It is not a de Polignac number, because 688645221 - 2¹⁹ = 688120933 is a prime.

It is a super-2 number, since 2×688645221² = 948464480812277682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688645201) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 916596 + ... + 917346.

It is an arithmetic number, because the mean of its divisors is an integer number (42921228).

Almost surely, 2^688645221 is an apocalyptic number.

It is an amenable number.

688645221 is a deficient number, since it is larger than the sum of its proper divisors (341464251).

688645221 is an equidigital number, since it uses as much as digits as its factorization.

688645221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1553 (or 802 counting only the distinct ones).

The product of its digits is 184320, while the sum is 42.

The square root of 688645221 is about 26242.0506249035. The cubic root of 688645221 is about 883.0768760981.

The spelling of 688645221 in words is "six hundred eighty-eight million, six hundred forty-five thousand, two hundred twenty-one".