166511621 has 2 divisors, whose sum is σ = 166511622. Its totient is φ = 166511620.

The previous prime is 166511599. The next prime is 166511623. The reversal of 166511621 is 126115661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 163584100 + 2927521 = 12790^2 + 1711^2 .

It is a cyclic number.

It is not a de Polignac number, because 166511621 - 2²² = 162317317 is a prime.

It is a super-2 number, since 2×166511621² = 55452239856095282, which contains 22 as substring.

Together with 166511623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (166511623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83255810 + 83255811.

It is an arithmetic number, because the mean of its divisors is an integer number (83255811).

Almost surely, 2^166511621 is an apocalyptic number.

It is an amenable number.

166511621 is a deficient number, since it is larger than the sum of its proper divisors (1).

166511621 is an equidigital number, since it uses as much as digits as its factorization.

166511621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2160, while the sum is 29.

The square root of 166511621 is about 12903.9381973102. The cubic root of 166511621 is about 550.1505053675.

The spelling of 166511621 in words is "one hundred sixty-six million, five hundred eleven thousand, six hundred twenty-one".