668692821 has 32 divisors (see below), whose sum is σ = 971268480. Its totient is φ = 407808000.

The previous prime is 668692811. The next prime is 668692831. The reversal of 668692821 is 128296866.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (668692811) and next prime (668692831).

It is not a de Polignac number, because 668692821 - 2⁶ = 668692757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668692811) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 234621 + ... + 237453.

It is an arithmetic number, because the mean of its divisors is an integer number (30352140).

Almost surely, 2^668692821 is an apocalyptic number.

It is an amenable number.

668692821 is a deficient number, since it is larger than the sum of its proper divisors (302575659).

668692821 is a wasteful number, since it uses less digits than its factorization.

668692821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2997.

The product of its digits is 497664, while the sum is 48.

The square root of 668692821 is about 25859.0955178251. The cubic root of 668692821 is about 874.4645740914.

The spelling of 668692821 in words is "six hundred sixty-eight million, six hundred ninety-two thousand, eight hundred twenty-one".