81690606 has 40 divisors (see below), whose sum is σ = 186959520. Its totient is φ = 26648352.

The previous prime is 81690599. The next prime is 81690613. The reversal of 81690606 is 60609618.

It is an interprime number because it is at equal distance from previous prime (81690599) and next prime (81690613).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 2250 + ... + 12978.

It is an arithmetic number, because the mean of its divisors is an integer number (4673988).

Almost surely, 2^81690606 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81690606, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (93479760).

81690606 is an abundant number, since it is smaller than the sum of its proper divisors (105268914).

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

81690606 is a wasteful number, since it uses less digits than its factorization.

81690606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10790 (or 10781 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 81690606 is about 9038.2855675178. The cubic root of 81690606 is about 433.9010548362.

The spelling of 81690606 in words is "eighty-one million, six hundred ninety thousand, six hundred six".