81399233 has 4 divisors (see below), whose sum is σ = 82205268. Its totient is φ = 80593200.

The previous prime is 81399229. The next prime is 81399239. The reversal of 81399233 is 33299318.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 75134224 + 6265009 = 8668^2 + 2503^2 .

It is a cyclic number.

It is not a de Polignac number, because 81399233 - 2² = 81399229 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81399239) 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, 402866 + ... + 403067.

It is an arithmetic number, because the mean of its divisors is an integer number (20551317).

Almost surely, 2^81399233 is an apocalyptic number.

It is an amenable number.

81399233 is a deficient number, since it is larger than the sum of its proper divisors (806035).

81399233 is a wasteful number, since it uses less digits than its factorization.

81399233 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 806034.

The product of its digits is 34992, while the sum is 38.

The square root of 81399233 is about 9022.1523485253. The cubic root of 81399233 is about 433.3845627139.

The spelling of 81399233 in words is "eighty-one million, three hundred ninety-nine thousand, two hundred thirty-three".