20990504161 has 9 divisors (see below), whose sum is σ = 23073958929. Its totient is φ = 19080827700.

The previous prime is 20990504159. The next prime is 20990504173. The reversal of 20990504161 is 16140509902.

The square root of 20990504161 is 144881.

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

It is not a de Polignac number, because 20990504161 - 2¹ = 20990504159 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20990504161.

It is not an unprimeable number, because it can be changed into a prime (20990504131) 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, 1587106 + ... + 1600276.

Almost surely, 2^20990504161 is an apocalyptic number.

20990504161 is the 144881-st square number.

20990504161 is the 72441-st centered octagonal number.

It is an amenable number.

20990504161 is a deficient number, since it is larger than the sum of its proper divisors (2083454768).

20990504161 is an frugal number, since it uses more digits than its factorization.

20990504161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26364 (or 13182 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 37.

The spelling of 20990504161 in words is "twenty billion, nine hundred ninety million, five hundred four thousand, one hundred sixty-one".