81219831 has 32 divisors (see below), whose sum is σ = 140894208. Its totient is φ = 40355040.

The previous prime is 81219793. The next prime is 81219841. The reversal of 81219831 is 13891218.

It is not a de Polignac number, because 81219831 - 2⁷ = 81219703 is a prime.

It is a super-2 number, since 2×81219831² = 13193321895337122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a junction number, because it is equal to n+sod(n) for n = 81219792 and 81219801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81219841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2331 + ... + 12956.

It is an arithmetic number, because the mean of its divisors is an integer number (4402944).

Almost surely, 2^81219831 is an apocalyptic number.

81219831 is a deficient number, since it is larger than the sum of its proper divisors (59674377).

81219831 is a wasteful number, since it uses less digits than its factorization.

81219831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15331.

The product of its digits is 3456, while the sum is 33.

The square root of 81219831 is about 9012.2045582643. The cubic root of 81219831 is about 433.0659387160.

It can be divided in two parts, 81 and 219831, that added together give a palindrome (219912).

The spelling of 81219831 in words is "eighty-one million, two hundred nineteen thousand, eight hundred thirty-one".