81261025 has 6 divisors (see below), whose sum is σ = 100763702. Its totient is φ = 65008800.

The previous prime is 81261023. The next prime is 81261029. The reversal of 81261025 is 52016218.

It can be written as a sum of positive squares in 3 ways, for example, as 1140624 + 80120401 = 1068^2 + 8951^2 .

It is not a de Polignac number, because 81261025 - 2¹ = 81261023 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25), and also a Moran number because the ratio is a prime number: 3250441 = 81261025 / (8 + 1 + 2 + 6 + 1 + 0 + 2 + 5).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81261023) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1625196 + ... + 1625245.

Almost surely, 2^81261025 is an apocalyptic number.

It is an amenable number.

81261025 is a deficient number, since it is larger than the sum of its proper divisors (19502677).

81261025 is a wasteful number, since it uses less digits than its factorization.

81261025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3250451 (or 3250446 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 81261025 is about 9014.4897248818. The cubic root of 81261025 is about 433.1391421150.

The spelling of 81261025 in words is "eighty-one million, two hundred sixty-one thousand, twenty-five".