81998025 has 12 divisors (see below), whose sum is σ = 135570192. Its totient is φ = 43732240.

The previous prime is 81997973. The next prime is 81998027. The reversal of 81998025 is 52089918.

It is a happy number.

It is not a de Polignac number, because 81998025 - 2¹⁶ = 81932489 is a prime.

It is a super-2 number, since 2×81998025² = 13447352207801250, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81998027) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 546579 + ... + 546728.

It is an arithmetic number, because the mean of its divisors is an integer number (11297516).

Almost surely, 2^81998025 is an apocalyptic number.

It is an amenable number.

81998025 is a deficient number, since it is larger than the sum of its proper divisors (53572167).

81998025 is a wasteful number, since it uses less digits than its factorization.

81998025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1093320 (or 1093315 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 81998025 is about 9055.2760863488. The cubic root of 81998025 is about 434.4446606013. Note that the first 3 decimals are identical.

The spelling of 81998025 in words is "eighty-one million, nine hundred ninety-eight thousand, twenty-five".