691089728 has 42 divisors (see below), whose sum is σ = 1595287386. Its totient is φ = 296179968.

The previous prime is 691089701. The next prime is 691089767. The reversal of 691089728 is 827980196.

It can be written as a sum of positive squares in only one way, i.e., 657819904 + 33269824 = 25648^2 + 5768^2 .

It is a super-2 number, since 2×691089728² = 955210024294227968, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 107051 + ... + 113322.

It is an arithmetic number, because the mean of its divisors is an integer number (37983033).

Almost surely, 2^691089728 is an apocalyptic number.

It is an amenable number.

691089728 is an abundant number, since it is smaller than the sum of its proper divisors (904197658).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

691089728 is a wasteful number, since it uses less digits than its factorization.

691089728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220399 (or 220382 counting only the distinct ones).

The product of its (nonzero) digits is 435456, while the sum is 50.

The square root of 691089728 is about 26288.5855077827. The cubic root of 691089728 is about 884.1205380155.

The spelling of 691089728 in words is "six hundred ninety-one million, eighty-nine thousand, seven hundred twenty-eight".