81105990 has 32 divisors (see below), whose sum is σ = 222462720. Its totient is φ = 18538464.

The previous prime is 81105977. The next prime is 81105991. The reversal of 81105990 is 9950118.

It is a super-2 number, since 2×81105990² = 13156363227760200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81105991) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 192900 + ... + 193319.

It is an arithmetic number, because the mean of its divisors is an integer number (6951960).

Almost surely, 2^81105990 is an apocalyptic number.

81105990 is an abundant number, since it is smaller than the sum of its proper divisors (141356730).

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

81105990 is a wasteful number, since it uses less digits than its factorization.

81105990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386236.

The product of its (nonzero) digits is 3240, while the sum is 33.

The square root of 81105990 is about 9005.8864083443. The cubic root of 81105990 is about 432.8635098641.

The spelling of 81105990 in words is "eighty-one million, one hundred five thousand, nine hundred ninety".