668525861 has 2 divisors, whose sum is σ = 668525862. Its totient is φ = 668525860.

The previous prime is 668525857. The next prime is 668525863. The reversal of 668525861 is 168525866.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 636603361 + 31922500 = 25231^2 + 5650^2 .

It is a cyclic number.

It is not a de Polignac number, because 668525861 - 2² = 668525857 is a prime.

Together with 668525863, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668525863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334262930 + 334262931.

It is an arithmetic number, because the mean of its divisors is an integer number (334262931).

Almost surely, 2^668525861 is an apocalyptic number.

It is an amenable number.

668525861 is a deficient number, since it is larger than the sum of its proper divisors (1).

668525861 is an equidigital number, since it uses as much as digits as its factorization.

668525861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 691200, while the sum is 47.

The square root of 668525861 is about 25855.8670517931. The cubic root of 668525861 is about 874.3917889233.

The spelling of 668525861 in words is "six hundred sixty-eight million, five hundred twenty-five thousand, eight hundred sixty-one".