81005825 has 12 divisors (see below), whose sum is σ = 100575408. Its totient is φ = 64722000.

The previous prime is 81005819. The next prime is 81005831. The reversal of 81005825 is 52850018.

It is an interprime number because it is at equal distance from previous prime (81005819) and next prime (81005831).

It is not a de Polignac number, because 81005825 - 2¹⁸ = 80743681 is a prime.

It is a Duffinian 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, 24734 + ... + 27816.

It is an arithmetic number, because the mean of its divisors is an integer number (8381284).

Almost surely, 2^81005825 is an apocalyptic number.

It is an amenable number.

81005825 is a deficient number, since it is larger than the sum of its proper divisors (19569583).

81005825 is a wasteful number, since it uses less digits than its factorization.

81005825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4144 (or 4139 counting only the distinct ones).

The product of its (nonzero) digits is 3200, while the sum is 29.

The square root of 81005825 is about 9000.3236052933. The cubic root of 81005825 is about 432.6852425766.

The spelling of 81005825 in words is "eighty-one million, five thousand, eight hundred twenty-five".