680651781 has 16 divisors (see below), whose sum is σ = 921637440. Its totient is φ = 446739840.

The previous prime is 680651759. The next prime is 680651819. The reversal of 680651781 is 187156086.

It is not a de Polignac number, because 680651781 - 2²² = 676457477 is a prime.

It is a super-2 number, since 2×680651781² = 926573693956943922, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (680651731) 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, 133051 + ... + 138071.

It is an arithmetic number, because the mean of its divisors is an integer number (57602340).

Almost surely, 2^680651781 is an apocalyptic number.

680651781 is the 15063-rd octagonal number.

It is an amenable number.

680651781 is a deficient number, since it is larger than the sum of its proper divisors (240985659).

680651781 is a wasteful number, since it uses less digits than its factorization.

680651781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5716.

The product of its (nonzero) digits is 80640, while the sum is 42.

The square root of 680651781 is about 26089.3039577525. The cubic root of 680651781 is about 879.6468025603.

The spelling of 680651781 in words is "six hundred eighty million, six hundred fifty-one thousand, seven hundred eighty-one".