81723564 has 144 divisors (see below), whose sum is σ = 236780544. Its totient is φ = 23587200.

The previous prime is 81723563. The next prime is 81723589. The reversal of 81723564 is 46532718.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81723563) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 623779 + ... + 623909.

Almost surely, 2^81723564 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 81723564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118390272).

81723564 is an abundant number, since it is smaller than the sum of its proper divisors (155056980).

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

81723564 is a wasteful number, since it uses less digits than its factorization.

81723564 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 228 (or 223 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 81723564 is about 9040.1086276659. The cubic root of 81723564 is about 433.9593993180.

The spelling of 81723564 in words is "eighty-one million, seven hundred twenty-three thousand, five hundred sixty-four".