16638162121 has 9 divisors (see below), whose sum is σ = 19355647149. Its totient is φ = 14260507884.

The previous prime is 16638162077. The next prime is 16638162131. The reversal of 16638162121 is 12126183661.

It is a happy number.

The square root of 16638162121 is 128989.

It is a perfect power (a square), and thus also a powerful number.

It is a de Polignac number, because none of the positive numbers 2^k-16638162121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (16638162131) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 893710 + ... + 912136.

It is an arithmetic number, because the mean of its divisors is an integer number (2150627461).

Almost surely, 2^16638162121 is an apocalyptic number.

16638162121 is the 128989-th square number.

16638162121 is the 64495-th centered octagonal number.

It is an amenable number.

16638162121 is a deficient number, since it is larger than the sum of its proper divisors (2717485028).

16638162121 is an frugal number, since it uses more digits than its factorization.

16638162121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36868 (or 18434 counting only the distinct ones).

The product of its digits is 20736, while the sum is 37.

Multiplying 16638162121 by its product of digits (20736), we get a square (345008929741056 = 18574416²).

The spelling of 16638162121 in words is "sixteen billion, six hundred thirty-eight million, one hundred sixty-two thousand, one hundred twenty-one".