17921980129 has 3 divisors (see below), whose sum is σ = 17922114003. Its totient is φ = 17921846256.

The previous prime is 17921980123. The next prime is 17921980163. The reversal of 17921980129 is 92108912971.

It is a happy number.

The square root of 17921980129 is 133873.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 92108912971 = 156241 ⋅589531.

It can be written as a sum of positive squares in only one way, i.e., 11736472225 + 6185507904 = 108335^2 + 78648^2 .

It is not a de Polignac number, because 17921980129 - 2⁷ = 17921980001 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (17921980123) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 66937 + ... + 200809.

It is an arithmetic number, because the mean of its divisors is an integer number (5974038001).

Almost surely, 2^17921980129 is an apocalyptic number.

17921980129 is the 133873-rd square number.

17921980129 is the 66937-th centered octagonal number.

It is an amenable number.

17921980129 is a deficient number, since it is larger than the sum of its proper divisors (133874).

17921980129 is an frugal number, since it uses more digits than its factorization.

17921980129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267746 (or 133873 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 49.

Multiplying 17921980129 by its sum of digits (49), we get a square (878177026321 = 937111²).

The spelling of 17921980129 in words is "seventeen billion, nine hundred twenty-one million, nine hundred eighty thousand, one hundred twenty-nine".