81199231 has 4 divisors (see below), whose sum is σ = 81349864. Its totient is φ = 81048600.

The previous prime is 81199211. The next prime is 81199247. The reversal of 81199231 is 13299118.

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 81199231 - 2¹⁷ = 81068159 is a prime.

It is a super-2 number, since 2×81199231² = 13186630229982722, 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 (81199211) 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, 74505 + ... + 75586.

It is an arithmetic number, because the mean of its divisors is an integer number (20337466).

Almost surely, 2^81199231 is an apocalyptic number.

81199231 is a deficient number, since it is larger than the sum of its proper divisors (150633).

81199231 is a wasteful number, since it uses less digits than its factorization.

81199231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150632.

The product of its digits is 3888, while the sum is 34.

The square root of 81199231 is about 9011.0615911778. The cubic root of 81199231 is about 433.0293224013.

The spelling of 81199231 in words is "eighty-one million, one hundred ninety-nine thousand, two hundred thirty-one".