691981825 has 6 divisors (see below), whose sum is σ = 858057494. Its totient is φ = 553585440.

The previous prime is 691981769. The next prime is 691981831. The reversal of 691981825 is 528189196.

It can be written as a sum of positive squares in 3 ways, for example, as 212897281 + 479084544 = 14591^2 + 21888^2 .

It is not a de Polignac number, because 691981825 - 2¹¹ = 691979777 is a prime.

It is a super-3 number, since 3×691981825³ (a number of 27 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian 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, 13839612 + ... + 13839661.

Almost surely, 2^691981825 is an apocalyptic number.

It is an amenable number.

691981825 is a deficient number, since it is larger than the sum of its proper divisors (166075669).

691981825 is a wasteful number, since it uses less digits than its factorization.

691981825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27679283 (or 27679278 counting only the distinct ones).

The product of its digits is 311040, while the sum is 49.

The square root of 691981825 is about 26305.5474187480. The cubic root of 691981825 is about 884.5007984051.

The spelling of 691981825 in words is "six hundred ninety-one million, nine hundred eighty-one thousand, eight hundred twenty-five".