81005425 has 24 divisors (see below), whose sum is σ = 110992896. Its totient is φ = 58333440.

The previous prime is 81005401. The next prime is 81005429. The reversal of 81005425 is 52450018.

It is not a de Polignac number, because 81005425 - 2²⁵ = 47450993 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81005425.

It is not an unprimeable number, because it can be changed into a prime (81005429) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5632 + ... + 13918.

It is an arithmetic number, because the mean of its divisors is an integer number (4624704).

Almost surely, 2^81005425 is an apocalyptic number.

81005425 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81005425 is a deficient number, since it is larger than the sum of its proper divisors (29987471).

81005425 is a wasteful number, since it uses less digits than its factorization.

81005425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8337 (or 8332 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 81005425 is about 9000.3013838427. The cubic root of 81005425 is about 432.6845303876.

The spelling of 81005425 in words is "eighty-one million, five thousand, four hundred twenty-five".