81423744 has 64 divisors (see below), whose sum is σ = 229022640. Its totient is φ = 25542656.

The previous prime is 81423743. The next prime is 81423779. The reversal of 81423744 is 44732418.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81423743) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 292 + ... + 12764.

Almost surely, 2^81423744 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81423744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (114511320).

81423744 is an abundant number, since it is smaller than the sum of its proper divisors (147598896).

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

81423744 is a wasteful number, since it uses less digits than its factorization.

81423744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12507 (or 12495 counting only the distinct ones).

The product of its digits is 21504, while the sum is 33.

The square root of 81423744 is about 9023.5106250284. The cubic root of 81423744 is about 433.4280587132.

The spelling of 81423744 in words is "eighty-one million, four hundred twenty-three thousand, seven hundred forty-four".