161656021 has 2 divisors, whose sum is σ = 161656022. Its totient is φ = 161656020.

The previous prime is 161656013. The next prime is 161656031. The reversal of 161656021 is 120656161.

161656021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 124567921 + 37088100 = 11161^2 + 6090^2 .

It is an emirp because it is prime and its reverse (120656161) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 161656021 - 2³ = 161656013 is a prime.

It is a super-2 number, since 2×161656021² = 52265338251104882, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161656031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80828010 + 80828011.

It is an arithmetic number, because the mean of its divisors is an integer number (80828011).

Almost surely, 2^161656021 is an apocalyptic number.

It is an amenable number.

161656021 is a deficient number, since it is larger than the sum of its proper divisors (1).

161656021 is an equidigital number, since it uses as much as digits as its factorization.

161656021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 28.

The square root of 161656021 is about 12714.4021094191. The cubic root of 161656021 is about 544.7500702921.

The spelling of 161656021 in words is "one hundred sixty-one million, six hundred fifty-six thousand, twenty-one".