681639887 has 4 divisors (see below), whose sum is σ = 690268320. Its totient is φ = 673011456.

The previous prime is 681639851. The next prime is 681639899. The reversal of 681639887 is 788936186.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 681639887 - 2¹⁰ = 681638863 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 (681639817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4314098 + ... + 4314255.

It is an arithmetic number, because the mean of its divisors is an integer number (172567080).

Almost surely, 2^681639887 is an apocalyptic number.

681639887 is a deficient number, since it is larger than the sum of its proper divisors (8628433).

681639887 is an equidigital number, since it uses as much as digits as its factorization.

681639887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8628432.

The product of its digits is 3483648, while the sum is 56.

The square root of 681639887 is about 26108.2340842884. The cubic root of 681639887 is about 880.0722594762.

The spelling of 681639887 in words is "six hundred eighty-one million, six hundred thirty-nine thousand, eight hundred eighty-seven".