81266591 has 8 divisors (see below), whose sum is σ = 97764480. Its totient is φ = 65990808.

The previous prime is 81266587. The next prime is 81266597. The reversal of 81266591 is 19566218.

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 81266591 - 2² = 81266587 is a prime.

It is a super-2 number, since 2×81266591² = 13208517625522562, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81266597) 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, 305381 + ... + 305646.

It is an arithmetic number, because the mean of its divisors is an integer number (12220560).

Almost surely, 2^81266591 is an apocalyptic number.

81266591 is a deficient number, since it is larger than the sum of its proper divisors (16497889).

81266591 is a wasteful number, since it uses less digits than its factorization.

81266591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 611053.

The product of its digits is 25920, while the sum is 38.

The square root of 81266591 is about 9014.7984447796. The cubic root of 81266591 is about 433.1490312241.

The spelling of 81266591 in words is "eighty-one million, two hundred sixty-six thousand, five hundred ninety-one".