681618640 has 40 divisors (see below), whose sum is σ = 1594886760. Its totient is φ = 270905856.

The previous prime is 681618629. The next prime is 681618647. The reversal of 681618640 is 46816186.

It can be written as a sum of positive squares in 4 ways, for example, as 128051856 + 553566784 = 11316^2 + 23528^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a junction number, because it is equal to n+sod(n) for n = 681618593 and 681618602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681618647) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 14575 + ... + 39694.

It is an arithmetic number, because the mean of its divisors is an integer number (39872169).

Almost surely, 2^681618640 is an apocalyptic number.

It is an amenable number.

681618640 is an abundant number, since it is smaller than the sum of its proper divisors (913268120).

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

681618640 is a wasteful number, since it uses less digits than its factorization.

681618640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54439 (or 54433 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 40.

The square root of 681618640 is about 26107.8271788366. The cubic root of 681618640 is about 880.0631153079.

The spelling of 681618640 in words is "six hundred eighty-one million, six hundred eighteen thousand, six hundred forty".