81690642 has 48 divisors (see below), whose sum is σ = 199330560. Its totient is φ = 23954400.

The previous prime is 81690629. The next prime is 81690647. The reversal of 81690642 is 24609618.

81690642 is a `hidden beast` number, since 8 + 1 + 6 + 9 + 0 + 642 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 81690597 and 81690606.

It is not an unprimeable number, because it can be changed into a prime (81690647) 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, 517 + ... + 12792.

It is an arithmetic number, because the mean of its divisors is an integer number (4152720).

Almost surely, 2^81690642 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81690642, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99665280).

81690642 is an abundant number, since it is smaller than the sum of its proper divisors (117639918).

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

81690642 is a wasteful number, since it uses less digits than its factorization.

81690642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13359 (or 13356 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 36.

The square root of 81690642 is about 9038.2875590457. The cubic root of 81690642 is about 433.9011185744.

The spelling of 81690642 in words is "eighty-one million, six hundred ninety thousand, six hundred forty-two".