691513945 has 4 divisors (see below), whose sum is σ = 829816740. Its totient is φ = 553211152.

The previous prime is 691513937. The next prime is 691513957. The reversal of 691513945 is 549315196.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 433847241 + 257666704 = 20829^2 + 16052^2 .

It is a cyclic number.

It is not a de Polignac number, because 691513945 - 2³ = 691513937 is a prime.

It is a super-2 number, since 2×691513945² = 956383072258926050, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 69151390 + ... + 69151399.

It is an arithmetic number, because the mean of its divisors is an integer number (207454185).

Almost surely, 2^691513945 is an apocalyptic number.

It is an amenable number.

691513945 is a deficient number, since it is larger than the sum of its proper divisors (138302795).

691513945 is a wasteful number, since it uses less digits than its factorization.

691513945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138302794.

The product of its digits is 145800, while the sum is 43.

The square root of 691513945 is about 26296.6527337606. The cubic root of 691513945 is about 884.3014032160.

The spelling of 691513945 in words is "six hundred ninety-one million, five hundred thirteen thousand, nine hundred forty-five".