81813120 has 64 divisors (see below), whose sum is σ = 260785440. Its totient is φ = 21816320.

The previous prime is 81813119. The next prime is 81813143. The reversal of 81813120 is 2131818.

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

It is a hoax number, since the sum of its digits (24) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19386 + ... + 23225.

Almost surely, 2^81813120 is an apocalyptic number.

81813120 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81813120 is an abundant number, since it is smaller than the sum of its proper divisors (178972320).

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

81813120 is a wasteful number, since it uses less digits than its factorization.

81813120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42633 (or 42621 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 24.

The square root of 81813120 is about 9045.0605304774. The cubic root of 81813120 is about 434.1178582274.

Adding to 81813120 its reverse (2131818), we get a palindrome (83944938).

The spelling of 81813120 in words is "eighty-one million, eight hundred thirteen thousand, one hundred twenty".