681993637 has 6 divisors (see below), whose sum is σ = 734556102. Its totient is φ = 629445672.

The previous prime is 681993629. The next prime is 681993643. The reversal of 681993637 is 736399186.

It can be written as a sum of positive squares in only one way, i.e., 472149441 + 209844196 = 21729^2 + 14486^2 .

It is not a de Polignac number, because 681993637 - 2³ = 681993629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (681993617) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 90538 + ... + 97780.

It is an arithmetic number, because the mean of its divisors is an integer number (122426017).

Almost surely, 2^681993637 is an apocalyptic number.

It is an amenable number.

681993637 is a deficient number, since it is larger than the sum of its proper divisors (52562465).

681993637 is an frugal number, since it uses more digits than its factorization.

681993637 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14499 (or 7256 counting only the distinct ones).

The product of its digits is 1469664, while the sum is 52.

The square root of 681993637 is about 26115.0078881857. The cubic root of 681993637 is about 880.2244765667.

Multiplying 681993637 by its sum of digits (52), we get a square (35463669124 = 188318²).

The spelling of 681993637 in words is "six hundred eighty-one million, nine hundred ninety-three thousand, six hundred thirty-seven".