81859820 has 24 divisors (see below), whose sum is σ = 196463904. Its totient is φ = 28066176.

The previous prime is 81859801. The next prime is 81859823. The reversal of 81859820 is 2895818.

It is not an unprimeable number, because it can be changed into a prime (81859823) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 292217 + ... + 292496.

It is an arithmetic number, because the mean of its divisors is an integer number (8185996).

Almost surely, 2^81859820 is an apocalyptic number.

It is an amenable number.

81859820 is an abundant number, since it is smaller than the sum of its proper divisors (114604084).

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

81859820 is a wasteful number, since it uses less digits than its factorization.

81859820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 584729 (or 584727 counting only the distinct ones).

The product of its (nonzero) digits is 46080, while the sum is 41.

The square root of 81859820 is about 9047.6416816759. The cubic root of 81859820 is about 434.2004425683.

The spelling of 81859820 in words is "eighty-one million, eight hundred fifty-nine thousand, eight hundred twenty".