691780640 has 24 divisors (see below), whose sum is σ = 1634332140. Its totient is φ = 276712192.

The previous prime is 691780571. The next prime is 691780657. The reversal of 691780640 is 46087196.

It can be written as a sum of positive squares in 2 ways, for example, as 649842064 + 41938576 = 25492^2 + 6476^2 .

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, 2161655 + ... + 2161974.

Almost surely, 2^691780640 is an apocalyptic number.

It is an amenable number.

691780640 is an abundant number, since it is smaller than the sum of its proper divisors (942551500).

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

691780640 is a wasteful number, since it uses less digits than its factorization.

691780640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4323644 (or 4323636 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 41.

The square root of 691780640 is about 26301.7231374676. The cubic root of 691780640 is about 884.4150709409.

The spelling of 691780640 in words is "six hundred ninety-one million, seven hundred eighty thousand, six hundred forty".