81533444 has 6 divisors (see below), whose sum is σ = 142683534. Its totient is φ = 40766720.

The previous prime is 81533437. The next prime is 81533449. The reversal of 81533444 is 44433518.

It can be written as a sum of positive squares in only one way, i.e., 77968900 + 3564544 = 8830^2 + 1888^2 .

It is a super-2 number, since 2×81533444² = 13295404981002272, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81533444.

It is not an unprimeable number, because it can be changed into a prime (81533449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10191677 + ... + 10191684.

It is an arithmetic number, because the mean of its divisors is an integer number (23780589).

Almost surely, 2^81533444 is an apocalyptic number.

It is an amenable number.

81533444 is a deficient number, since it is larger than the sum of its proper divisors (61150090).

81533444 is a wasteful number, since it uses less digits than its factorization.

81533444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20383365 (or 20383363 counting only the distinct ones).

The product of its digits is 23040, while the sum is 32.

The square root of 81533444 is about 9029.5871444934. The cubic root of 81533444 is about 433.6226199830.

The spelling of 81533444 in words is "eighty-one million, five hundred thirty-three thousand, four hundred forty-four".