81257905 has 8 divisors (see below), whose sum is σ = 97560000. Its totient is φ = 64972656.

The previous prime is 81257903. The next prime is 81257921. The reversal of 81257905 is 50975218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81257905 - 2¹ = 81257903 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81257903) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12286 + ... + 17704.

It is an arithmetic number, because the mean of its divisors is an integer number (12195000).

Almost surely, 2^81257905 is an apocalyptic number.

It is an amenable number.

81257905 is a deficient number, since it is larger than the sum of its proper divisors (16302095).

81257905 is a wasteful number, since it uses less digits than its factorization.

81257905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8423.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 81257905 is about 9014.3166685002. The cubic root of 81257905 is about 433.1335986152.

The spelling of 81257905 in words is "eighty-one million, two hundred fifty-seven thousand, nine hundred five".