166321621 has 2 divisors, whose sum is σ = 166321622. Its totient is φ = 166321620.

The previous prime is 166321601. The next prime is 166321633. The reversal of 166321621 is 126123661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 90440100 + 75881521 = 9510^2 + 8711^2 .

It is a cyclic number.

It is not a de Polignac number, because 166321621 - 2¹⁵ = 166288853 is a prime.

It is a super-2 number, since 2×166321621² = 55325763224135282, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 166321621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166321601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83160810 + 83160811.

It is an arithmetic number, because the mean of its divisors is an integer number (83160811).

Almost surely, 2^166321621 is an apocalyptic number.

It is an amenable number.

166321621 is a deficient number, since it is larger than the sum of its proper divisors (1).

166321621 is an equidigital number, since it uses as much as digits as its factorization.

166321621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2592, while the sum is 28.

The square root of 166321621 is about 12896.5740024241. The cubic root of 166321621 is about 549.9411738737.

The spelling of 166321621 in words is "one hundred sixty-six million, three hundred twenty-one thousand, six hundred twenty-one".