81861880 has 32 divisors (see below), whose sum is σ = 193885200. Its totient is φ = 31021056.

The previous prime is 81861877. The next prime is 81861883. The reversal of 81861880 is 8816818.

81861880 = T₁₂₆₅ + T₁₂₆₆ + ... + T₁₃₅₉.

It is an interprime number because it is at equal distance from previous prime (81861877) and next prime (81861883).

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81861883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53097 + ... + 54616.

Almost surely, 2^81861880 is an apocalyptic number.

It is an amenable number.

81861880 is an abundant number, since it is smaller than the sum of its proper divisors (112023320).

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

81861880 is a wasteful number, since it uses less digits than its factorization.

81861880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107743 (or 107739 counting only the distinct ones).

The product of its (nonzero) digits is 24576, while the sum is 40.

The square root of 81861880 is about 9047.7555227802. The cubic root of 81861880 is about 434.2040847516.

The spelling of 81861880 in words is "eighty-one million, eight hundred sixty-one thousand, eight hundred eighty".