18978093121 has 9 divisors (see below), whose sum is σ = 20552182281. Its totient is φ = 17516586672.

The previous prime is 18978093091. The next prime is 18978093139. The reversal of 18978093121 is 12139087981.

The square root of 18978093121 is 137761.

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

It can be written as a sum of positive squares in 4 ways, for example, as 13389035521 + 5589057600 = 115711^2 + 74760^2 .

It is not a de Polignac number, because 18978093121 - 2¹¹ = 18978091073 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18978093221) 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, 1785595 + ... + 1796191.

It is an arithmetic number, because the mean of its divisors is an integer number (2283575809).

Almost surely, 2^18978093121 is an apocalyptic number.

18978093121 is the 137761-st square number.

18978093121 is the 68881-st centered octagonal number.

It is an amenable number.

18978093121 is a deficient number, since it is larger than the sum of its proper divisors (1574089160).

18978093121 is an frugal number, since it uses more digits than its factorization.

18978093121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21220 (or 10610 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 49.

Multiplying 18978093121 by its sum of digits (49), we get a square (929926562929 = 964327²).

The spelling of 18978093121 in words is "eighteen billion, nine hundred seventy-eight million, ninety-three thousand, one hundred twenty-one".