691305021 has 12 divisors (see below), whose sum is σ = 1089329280. Its totient is φ = 418972680.

The previous prime is 691305007. The next prime is 691305073. The reversal of 691305021 is 120503196.

It is not a de Polignac number, because 691305021 - 2⁵ = 691304989 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691305421) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3491341 + ... + 3491538.

It is an arithmetic number, because the mean of its divisors is an integer number (90777440).

Almost surely, 2^691305021 is an apocalyptic number.

It is an amenable number.

691305021 is a deficient number, since it is larger than the sum of its proper divisors (398024259).

691305021 is a wasteful number, since it uses less digits than its factorization.

691305021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6982896 (or 6982893 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 691305021 is about 26292.6799889247. The cubic root of 691305021 is about 884.2123375763.

The spelling of 691305021 in words is "six hundred ninety-one million, three hundred five thousand, twenty-one".