681640351 has 16 divisors (see below), whose sum is σ = 815961600. Its totient is φ = 556747488.

The previous prime is 681640319. The next prime is 681640373. The reversal of 681640351 is 153046186.

681640351 = 3109² + 3110² + ... + 3177².

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 681640351 - 2⁵ = 681640319 is a prime.

It is a super-2 number, since 2×681640351² = 929267136222806402, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681640051) 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, 35440 + ... + 51178.

It is an arithmetic number, because the mean of its divisors is an integer number (50997600).

Almost surely, 2^681640351 is an apocalyptic number.

681640351 is a deficient number, since it is larger than the sum of its proper divisors (134321249).

681640351 is a wasteful number, since it uses less digits than its factorization.

681640351 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16038.

The product of its (nonzero) digits is 17280, while the sum is 34.

The square root of 681640351 is about 26108.2429703724. The cubic root of 681640351 is about 880.0724591678.

The spelling of 681640351 in words is "six hundred eighty-one million, six hundred forty thousand, three hundred fifty-one".