691661408 has 48 divisors (see below), whose sum is σ = 1439046000. Its totient is φ = 326333952.

The previous prime is 691661381. The next prime is 691661413. The reversal of 691661408 is 804166196.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161438 + ... + 165666.

It is an arithmetic number, because the mean of its divisors is an integer number (29980125).

Almost surely, 2^691661408 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 691661408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (719523000).

691661408 is an abundant number, since it is smaller than the sum of its proper divisors (747384592).

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

691661408 is a wasteful number, since it uses less digits than its factorization.

691661408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4527 (or 4519 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 41.

The square root of 691661408 is about 26299.4564202380. The cubic root of 691661408 is about 884.3642568386.

The spelling of 691661408 in words is "six hundred ninety-one million, six hundred sixty-one thousand, four hundred eight".