81862020 has 72 divisors (see below), whose sum is σ = 249279576. Its totient is φ = 21745152.

The previous prime is 81861977. The next prime is 81862049. The reversal of 81862020 is 2026818.

81862020 is a `hidden beast` number, since 8 + 18 + 620 + 20 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 6380676 + 75481344 = 2526^2 + 8688^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 55614 + ... + 57066.

Almost surely, 2^81862020 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81862020, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124639788).

81862020 is an abundant number, since it is smaller than the sum of its proper divisors (167417556).

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

81862020 is a wasteful number, since it uses less digits than its factorization.

81862020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1781 (or 1776 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 81862020 is about 9047.7632595023. The cubic root of 81862020 is about 434.2043322764.

Adding to 81862020 its reverse (2026818), we get a palindrome (83888838).

The spelling of 81862020 in words is "eighty-one million, eight hundred sixty-two thousand, twenty".