81813774 has 48 divisors (see below), whose sum is σ = 193325184. Its totient is φ = 22610160.

The previous prime is 81813769. The next prime is 81813803. The reversal of 81813774 is 47731818.

81813774 = T₁₅₈₀ + T₁₅₈₁ + ... + T₁₆₄₂.

It is a super-2 number, since 2×81813774² = 13386987232246152, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39349 + ... + 41375.

It is an arithmetic number, because the mean of its divisors is an integer number (4027608).

Almost surely, 2^81813774 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81813774, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (96662592).

81813774 is an abundant number, since it is smaller than the sum of its proper divisors (111511410).

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

81813774 is a wasteful number, since it uses less digits than its factorization.

81813774 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2101 (or 2070 counting only the distinct ones).

The product of its digits is 37632, while the sum is 39.

The square root of 81813774 is about 9045.0966827337. The cubic root of 81813774 is about 434.1190149788.

The spelling of 81813774 in words is "eighty-one million, eight hundred thirteen thousand, seven hundred seventy-four".