161564021 has 2 divisors, whose sum is σ = 161564022. Its totient is φ = 161564020.

The previous prime is 161563999. The next prime is 161564047. The reversal of 161564021 is 120465161.

It is an a-pointer prime, because the next prime (161564047) can be obtained adding 161564021 to its sum of digits (26).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 153412996 + 8151025 = 12386^2 + 2855^2 .

It is a cyclic number.

It is not a de Polignac number, because 161564021 - 2²² = 157369717 is a prime.

It is a super-2 number, since 2×161564021² = 52205865763376882, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (161563021) 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, 80782010 + 80782011.

It is an arithmetic number, because the mean of its divisors is an integer number (80782011).

Almost surely, 2^161564021 is an apocalyptic number.

It is an amenable number.

161564021 is a deficient number, since it is larger than the sum of its proper divisors (1).

161564021 is an equidigital number, since it uses as much as digits as its factorization.

161564021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1440, while the sum is 26.

The square root of 161564021 is about 12710.7836501138. The cubic root of 161564021 is about 544.6467098430.

The spelling of 161564021 in words is "one hundred sixty-one million, five hundred sixty-four thousand, twenty-one".