691995621 has 8 divisors (see below), whose sum is σ = 923709280. Its totient is φ = 460806192.

The previous prime is 691995611. The next prime is 691995649. The reversal of 691995621 is 126599196.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 691995621 - 2¹⁵ = 691962853 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691995611) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127966 + ... + 133263.

It is an arithmetic number, because the mean of its divisors is an integer number (115463660).

Almost surely, 2^691995621 is an apocalyptic number.

It is an amenable number.

691995621 is a deficient number, since it is larger than the sum of its proper divisors (231713659).

691995621 is a wasteful number, since it uses less digits than its factorization.

691995621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 262115.

The product of its digits is 262440, while the sum is 48.

The square root of 691995621 is about 26305.8096434989. The cubic root of 691995621 is about 884.5066764458.

The spelling of 691995621 in words is "six hundred ninety-one million, nine hundred ninety-five thousand, six hundred twenty-one".