781616640 has 480 divisors, whose sum is σ = 3045233664. Its totient is φ = 170311680.

The previous prime is 781616639. The next prime is 781616653. The reversal of 781616640 is 46616187.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (480).

It is a super-2 number, since 2×781616640² = 1221849143849779200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 11665887 + ... + 11665953.

Almost surely, 2^781616640 is an apocalyptic number.

781616640 is a gapful number since it is divisible by the number (70) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 781616640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1522616832).

781616640 is an abundant number, since it is smaller than the sum of its proper divisors (2263617024).

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

781616640 is a wasteful number, since it uses less digits than its factorization.

781616640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138 (or 115 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 39.

The square root of 781616640 is about 27957.4076051411. The cubic root of 781616640 is about 921.1519282140.

The spelling of 781616640 in words is "seven hundred eighty-one million, six hundred sixteen thousand, six hundred forty".