668817551 has 2 divisors, whose sum is σ = 668817552. Its totient is φ = 668817550.

The previous prime is 668817503. The next prime is 668817557. The reversal of 668817551 is 155718866.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 668817551 - 2²⁶ = 601708687 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 668817496 and 668817505.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668817557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334408775 + 334408776.

It is an arithmetic number, because the mean of its divisors is an integer number (334408776).

Almost surely, 2^668817551 is an apocalyptic number.

668817551 is a deficient number, since it is larger than the sum of its proper divisors (1).

668817551 is an equidigital number, since it uses as much as digits as its factorization.

668817551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 47.

The square root of 668817551 is about 25861.5071293225. The cubic root of 668817551 is about 874.5189414491.

The spelling of 668817551 in words is "six hundred sixty-eight million, eight hundred seventeen thousand, five hundred fifty-one".