81870642 has 64 divisors (see below), whose sum is σ = 211507200. Its totient is φ = 22988880.

The previous prime is 81870641. The next prime is 81870643. The reversal of 81870642 is 24607818.

81870642 is a `hidden beast` number, since 8 + 1 + 8 + 7 + 0 + 642 = 666.

It is an interprime number because it is at equal distance from previous prime (81870641) and next prime (81870643).

It is a junction number, because it is equal to n+sod(n) for n = 81870597 and 81870606.

It is not an unprimeable number, because it can be changed into a prime (81870641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20467 + ... + 24137.

It is an arithmetic number, because the mean of its divisors is an integer number (3304800).

Almost surely, 2^81870642 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81870642, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (105753600).

81870642 is an abundant number, since it is smaller than the sum of its proper divisors (129636558).

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

81870642 is a wasteful number, since it uses less digits than its factorization.

81870642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3748 (or 3742 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 36.

The square root of 81870642 is about 9048.2397183099. The cubic root of 81870642 is about 434.2195757244.

The spelling of 81870642 in words is "eighty-one million, eight hundred seventy thousand, six hundred forty-two".