691906906 has 4 divisors (see below), whose sum is σ = 1037860362. Its totient is φ = 345953452.

The previous prime is 691906883. The next prime is 691906931. The reversal of 691906906 is 609609196.

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

It can be written as a sum of positive squares in only one way, i.e., 686911681 + 4995225 = 26209^2 + 2235^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 172976725 + ... + 172976728.

Almost surely, 2^691906906 is an apocalyptic number.

691906906 is a deficient number, since it is larger than the sum of its proper divisors (345953456).

691906906 is a wasteful number, since it uses less digits than its factorization.

691906906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345953455.

The product of its (nonzero) digits is 157464, while the sum is 46.

The square root of 691906906 is about 26304.1233649784. The cubic root of 691906906 is about 884.4688764169.

The spelling of 691906906 in words is "six hundred ninety-one million, nine hundred six thousand, nine hundred six".