81425891 has 4 divisors (see below), whose sum is σ = 81631392. Its totient is φ = 81220392.

The previous prime is 81425831. The next prime is 81425899. The reversal of 81425891 is 19852418.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81425891 - 2²² = 77231587 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81425899) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 102155 + ... + 102948.

It is an arithmetic number, because the mean of its divisors is an integer number (20407848).

Almost surely, 2^81425891 is an apocalyptic number.

81425891 is a deficient number, since it is larger than the sum of its proper divisors (205501).

81425891 is a wasteful number, since it uses less digits than its factorization.

81425891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205500.

The product of its digits is 23040, while the sum is 38.

The square root of 81425891 is about 9023.6295912454. The cubic root of 81425891 is about 433.4318682567.

The spelling of 81425891 in words is "eighty-one million, four hundred twenty-five thousand, eight hundred ninety-one".