81991452 has 12 divisors (see below), whose sum is σ = 191313416. Its totient is φ = 27330480.

The previous prime is 81991433. The next prime is 81991457. The reversal of 81991452 is 25419918.

It is a tau number, because it is divible by the number of its divisors (12).

It is a self number, because there is not a number n which added to its sum of digits gives 81991452.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81991457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3416299 + ... + 3416322.

Almost surely, 2^81991452 is an apocalyptic number.

It is an amenable number.

81991452 is an abundant number, since it is smaller than the sum of its proper divisors (109321964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81991452 is a wasteful number, since it uses less digits than its factorization.

81991452 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6832628 (or 6832626 counting only the distinct ones).

The product of its digits is 25920, while the sum is 39.

The square root of 81991452 is about 9054.9131414940. The cubic root of 81991452 is about 434.4330518621.

The spelling of 81991452 in words is "eighty-one million, nine hundred ninety-one thousand, four hundred fifty-two".