81259990 has 32 divisors (see below), whose sum is σ = 172560384. Its totient is φ = 26961120.

The previous prime is 81259987. The next prime is 81259999. The reversal of 81259990 is 9995218.

It is a Smith number, since the sum of its digits (43) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81259999) 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, 16554 + ... + 20893.

It is an arithmetic number, because the mean of its divisors is an integer number (5392512).

Almost surely, 2^81259990 is an apocalyptic number.

81259990 is an abundant number, since it is smaller than the sum of its proper divisors (91300394).

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

81259990 is a wasteful number, since it uses less digits than its factorization.

81259990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37492.

The product of its (nonzero) digits is 58320, while the sum is 43.

The square root of 81259990 is about 9014.4323171235. The cubic root of 81259990 is about 433.1373031813.

The spelling of 81259990 in words is "eighty-one million, two hundred fifty-nine thousand, nine hundred ninety".