18921378025 has 81 divisors (see below), whose sum is σ = 26874163407. Its totient is φ = 13205280000.

The previous prime is 18921378013. The next prime is 18921378043. The reversal of 18921378025 is 52087312981.

It is a happy number.

The square root of 18921378025 is 137555.

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

It can be written as a sum of positive squares in 13 ways, for example, as 14173616809 + 4747761216 = 119053^2 + 68904^2 .

It is not a de Polignac number, because 18921378025 - 2⁷ = 18921377897 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 80 ways as a sum of consecutive naturals, for example, 310186495 + ... + 310186555.

Almost surely, 2^18921378025 is an apocalyptic number.

18921378025 is the 137555-th square number.

18921378025 is the 68778-th centered octagonal number.

It is an amenable number.

18921378025 is a deficient number, since it is larger than the sum of its proper divisors (7952785382).

18921378025 is an equidigital number, since it uses as much as digits as its factorization.

18921378025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 236 (or 118 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 46.

The spelling of 18921378025 in words is "eighteen billion, nine hundred twenty-one million, three hundred seventy-eight thousand, twenty-five".