156166721 has 2 divisors, whose sum is σ = 156166722. Its totient is φ = 156166720.

The previous prime is 156166679. The next prime is 156166723. The reversal of 156166721 is 127661651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151167025 + 4999696 = 12295^2 + 2236^2 .

It is a cyclic number.

It is not a de Polignac number, because 156166721 - 2¹⁸ = 155904577 is a prime.

Together with 156166723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (156166723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 78083360 + 78083361.

It is an arithmetic number, because the mean of its divisors is an integer number (78083361).

Almost surely, 2^156166721 is an apocalyptic number.

It is an amenable number.

156166721 is a deficient number, since it is larger than the sum of its proper divisors (1).

156166721 is an equidigital number, since it uses as much as digits as its factorization.

156166721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15120, while the sum is 35.

The square root of 156166721 is about 12496.6683960166. The cubic root of 156166721 is about 538.5129652803.

The spelling of 156166721 in words is "one hundred fifty-six million, one hundred sixty-six thousand, seven hundred twenty-one".