81291672 has 288 divisors, whose sum is σ = 292131840. Its totient is φ = 19958400.

The previous prime is 81291659. The next prime is 81291673. The reversal of 81291672 is 27619218.

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81291673) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1890483 + ... + 1890525.

Almost surely, 2^81291672 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 81291672, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (146065920).

81291672 is an abundant number, since it is smaller than the sum of its proper divisors (210840168).

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

81291672 is a wasteful number, since it uses less digits than its factorization.

81291672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115 (or 97 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 81291672 is about 9016.1894390036. The cubic root of 81291672 is about 433.1935870220.

It can be divided in two parts, 8129 and 1672, that added together give a square (9801 = 99²).

The spelling of 81291672 in words is "eighty-one million, two hundred ninety-one thousand, six hundred seventy-two".