81275261 has 4 divisors (see below), whose sum is σ = 84808992. Its totient is φ = 77741532.

The previous prime is 81275251. The next prime is 81275263. The reversal of 81275261 is 16257218.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81275261 - 2²² = 77080957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81275263) 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, 1766831 + ... + 1766876.

It is an arithmetic number, because the mean of its divisors is an integer number (21202248).

Almost surely, 2^81275261 is an apocalyptic number.

It is an amenable number.

81275261 is a deficient number, since it is larger than the sum of its proper divisors (3533731).

81275261 is a wasteful number, since it uses less digits than its factorization.

81275261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3533730.

The product of its digits is 6720, while the sum is 32.

The square root of 81275261 is about 9015.2793079305. The cubic root of 81275261 is about 433.1644343088.

The spelling of 81275261 in words is "eighty-one million, two hundred seventy-five thousand, two hundred sixty-one".