156172021 has 2 divisors, whose sum is σ = 156172022. Its totient is φ = 156172020.

The previous prime is 156171991. The next prime is 156172061. The reversal of 156172021 is 120271651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 135140625 + 21031396 = 11625^2 + 4586^2 .

It is a cyclic number.

It is not a de Polignac number, because 156172021 - 2²³ = 147783413 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (156172061) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 78086010 + 78086011.

It is an arithmetic number, because the mean of its divisors is an integer number (78086011).

Almost surely, 2^156172021 is an apocalyptic number.

It is an amenable number.

156172021 is a deficient number, since it is larger than the sum of its proper divisors (1).

156172021 is an equidigital number, since it uses as much as digits as its factorization.

156172021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 840, while the sum is 25.

The square root of 156172021 is about 12496.8804507365. The cubic root of 156172021 is about 538.5190572449.

The spelling of 156172021 in words is "one hundred fifty-six million, one hundred seventy-two thousand, twenty-one".