668688157 has 2 divisors, whose sum is σ = 668688158. Its totient is φ = 668688156.

The previous prime is 668688133. The next prime is 668688173. The reversal of 668688157 is 751886866.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 455352921 + 213335236 = 21339^2 + 14606^2 .

It is a cyclic number.

It is not a de Polignac number, because 668688157 - 2¹⁵ = 668655389 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 668688098 and 668688107.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (668688107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334344078 + 334344079.

It is an arithmetic number, because the mean of its divisors is an integer number (334344079).

Almost surely, 2^668688157 is an apocalyptic number.

It is an amenable number.

668688157 is a deficient number, since it is larger than the sum of its proper divisors (1).

668688157 is an equidigital number, since it uses as much as digits as its factorization.

668688157 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3870720, while the sum is 55.

The square root of 668688157 is about 25859.0053366327. The cubic root of 668688157 is about 874.4625410142.

The spelling of 668688157 in words is "six hundred sixty-eight million, six hundred eighty-eight thousand, one hundred fifty-seven".