781664564 has 12 divisors (see below), whose sum is σ = 1393723044. Its totient is φ = 383457984.

The previous prime is 781664563. The next prime is 781664671. The reversal of 781664564 is 465466187.

It can be written as a sum of positive squares in 2 ways, for example, as 619611664 + 162052900 = 24892^2 + 12730^2 .

It is a super-2 number, since 2×781664564² = 1221998981226620192, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781664561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1843337 + ... + 1843760.

It is an arithmetic number, because the mean of its divisors is an integer number (116143587).

Almost surely, 2^781664564 is an apocalyptic number.

It is an amenable number.

781664564 is a deficient number, since it is larger than the sum of its proper divisors (612058480).

781664564 is a wasteful number, since it uses less digits than its factorization.

781664564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3687154 (or 3687152 counting only the distinct ones).

The product of its digits is 967680, while the sum is 47.

The square root of 781664564 is about 27958.2646814855. The cubic root of 781664564 is about 921.1707543156.

The spelling of 781664564 in words is "seven hundred eighty-one million, six hundred sixty-four thousand, five hundred sixty-four".