781645680 has 80 divisors (see below), whose sum is σ = 2692342560. Its totient is φ = 208438272.

The previous prime is 781645637. The next prime is 781645681. The reversal of 781645680 is 86546187.

It is a happy number.

781645680 is a `hidden beast` number, since 7 + 81 + 6 + 4 + 568 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×781645680² = 1221939938125324800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781645681) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 178777 + ... + 183096.

It is an arithmetic number, because the mean of its divisors is an integer number (33654282).

Almost surely, 2^781645680 is an apocalyptic number.

It is an amenable number.

781645680 is an abundant number, since it is smaller than the sum of its proper divisors (1910696880).

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

781645680 is a wasteful number, since it uses less digits than its factorization.

781645680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 361895 (or 361883 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The square root of 781645680 is about 27957.9269617760. The cubic root of 781645680 is about 921.1633361597.

The spelling of 781645680 in words is "seven hundred eighty-one million, six hundred forty-five thousand, six hundred eighty".