166519249921 has 2 divisors, whose sum is σ = 166519249922. Its totient is φ = 166519249920.

The previous prime is 166519249907. The next prime is 166519249933. The reversal of 166519249921 is 129942915661.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151390249921 + 15129000000 = 389089^2 + 123000^2 .

It is a cyclic number.

It is not a de Polignac number, because 166519249921 - 2⁹ = 166519249409 is a prime.

It is not a weakly prime, because it can be changed into another prime (166519249951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 83259624960 + 83259624961.

It is an arithmetic number, because the mean of its divisors is an integer number (83259624961).

Almost surely, 2^166519249921 is an apocalyptic number.

It is an amenable number.

166519249921 is a deficient number, since it is larger than the sum of its proper divisors (1).

166519249921 is an equidigital number, since it uses as much as digits as its factorization.

166519249921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2099520, while the sum is 55.

The spelling of 166519249921 in words is "one hundred sixty-six billion, five hundred nineteen million, two hundred forty-nine thousand, nine hundred twenty-one".