81000025 has 12 divisors (see below), whose sum is σ = 100551724. Its totient is φ = 64728000.

The previous prime is 81000013. The next prime is 81000037. The reversal of 81000025 is 52000018.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81000013) and next prime (81000037).

It can be written as a sum of positive squares in 6 ways, for example, as 49224256 + 31775769 = 7016^2 + 5637^2 .

It is not a de Polignac number, because 81000025 - 2²³ = 72611417 is a prime.

It is a super-2 number, since 2×81000025² = 13122008100001250, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 80999972 and 81000008.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 42595 + ... + 44455.

Almost surely, 2^81000025 is an apocalyptic number.

It is an amenable number.

81000025 is a deficient number, since it is larger than the sum of its proper divisors (19551699).

81000025 is a wasteful number, since it uses less digits than its factorization.

81000025 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3612 (or 3607 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 81000025 is about 9000.0013888888. The cubic root of 81000025 is about 432.6749156061.

It can be divided in two parts, 810000 and 25, that multiplied together give a square (20250000 = 4500²).

The spelling of 81000025 in words is "eighty-one million, twenty-five", and thus it is an aban number and an uban number.