81920025 has 144 divisors (see below), whose sum is σ = 178113600. Its totient is φ = 36748800.

The previous prime is 81920023. The next prime is 81920053. The reversal of 81920025 is 52002918.

It is not a de Polignac number, because 81920025 - 2¹ = 81920023 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81920021) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 1388446 + ... + 1388504.

It is an arithmetic number, because the mean of its divisors is an integer number (1236900).

Almost surely, 2^81920025 is an apocalyptic number.

81920025 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81920025 is an abundant number, since it is smaller than the sum of its proper divisors (96193575).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81920025 is a wasteful number, since it uses less digits than its factorization.

81920025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 117 (or 95 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The square root of 81920025 is about 9050.9681802556. The cubic root of 81920025 is about 434.3068628352.

The spelling of 81920025 in words is "eighty-one million, nine hundred twenty thousand, twenty-five".