81670590 has 48 divisors (see below), whose sum is σ = 215351136. Its totient is φ = 21470400.

The previous prime is 81670579. The next prime is 81670591. The reversal of 81670590 is 9507618.

81670590 is a `hidden beast` number, since 8 + 1 + 67 + 0 + 590 = 666.

81670590 is a nontrivial binomial coefficient, being equal to C(12781, 2).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81670591) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1 + ... + 12780.

It is an arithmetic number, because the mean of its divisors is an integer number (4486482).

Almost surely, 2^81670590 is an apocalyptic number.

81670590 is the 12780-th triangular number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81670590, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107675568).

81670590 is an abundant number, since it is smaller than the sum of its proper divisors (133680546).

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

81670590 is a wasteful number, since it uses less digits than its factorization.

81670590 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12865 (or 12862 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 36.

The square root of 81670590 is about 9037.1782100388. The cubic root of 81670590 is about 433.8656134990.

The spelling of 81670590 in words is "eighty-one million, six hundred seventy thousand, five hundred ninety".