81800261 has 4 divisors (see below), whose sum is σ = 81863232. Its totient is φ = 81737292.

The previous prime is 81800221. The next prime is 81800281. The reversal of 81800261 is 16200818.

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 a de Polignac number, because none of the positive numbers 2^k-81800261 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81800261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81800221) 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, 29495 + ... + 32148.

It is an arithmetic number, because the mean of its divisors is an integer number (20465808).

Almost surely, 2^81800261 is an apocalyptic number.

It is an amenable number.

81800261 is a deficient number, since it is larger than the sum of its proper divisors (62971).

81800261 is a wasteful number, since it uses less digits than its factorization.

81800261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62970.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 81800261 is about 9044.3496725856. The cubic root of 81800261 is about 434.0951128371.

The spelling of 81800261 in words is "eighty-one million, eight hundred thousand, two hundred sixty-one".