81628231 has 4 divisors (see below), whose sum is σ = 81683352. Its totient is φ = 81573112.

The previous prime is 81628223. The next prime is 81628249. The reversal of 81628231 is 13282618.

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 81628231 - 2³ = 81628223 is a prime.

It is a super-2 number, since 2×81628231² = 13326336192378722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81628193 and 81628202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81628201) 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, 25276 + ... + 28321.

It is an arithmetic number, because the mean of its divisors is an integer number (20420838).

Almost surely, 2^81628231 is an apocalyptic number.

81628231 is a deficient number, since it is larger than the sum of its proper divisors (55121).

81628231 is a wasteful number, since it uses less digits than its factorization.

81628231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55120.

The product of its digits is 4608, while the sum is 31.

The square root of 81628231 is about 9034.8343094935. The cubic root of 81628231 is about 433.7905914225.

The spelling of 81628231 in words is "eighty-one million, six hundred twenty-eight thousand, two hundred thirty-one".