18917149878225 has 135 divisors (see below), whose sum is σ = 36989707481067. Its totient is φ = 9556259951520.

The previous prime is 18917149878197. The next prime is 18917149878271. The reversal of 18917149878225 is 52287894171981.

The square root of 18917149878225 is 4349385.

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

18917149878225 is a `hidden beast` number, since 1 + 89 + 171 + 4 + 98 + 78 + 225 = 666.

It can be written as a sum of positive squares in only one way, i.e., 6810173956161 + 12106975922064 = 2609631^2 + 3479508^2 .

It is a tau number, because it is divible by the number of its divisors (135).

It is not a de Polignac number, because 18917149878225 - 2²⁵ = 18917116323793 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 134 ways as a sum of consecutive naturals, for example, 3718721632 + ... + 3718726718.

Almost surely, 2^{18917149878225} is an apocalyptic number.

18917149878225 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

18917149878225 is the 4349385-th square number.

18917149878225 is the 2174693-rd centered octagonal number.

It is an amenable number.

18917149878225 is a deficient number, since it is larger than the sum of its proper divisors (18072557602842).

18917149878225 is an frugal number, since it uses more digits than its factorization.

18917149878225 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10234 (or 5114 counting only the distinct ones).

The product of its digits is 162570240, while the sum is 72.

The spelling of 18917149878225 in words is "eighteen trillion, nine hundred seventeen billion, one hundred forty-nine million, eight hundred seventy-eight thousand, two hundred twenty-five".