81435780 has 120 divisors (see below), whose sum is σ = 270586008. Its totient is φ = 20431872.

The previous prime is 81435769. The next prime is 81435803. The reversal of 81435780 is 8753418.

81435780 is a `hidden beast` number, since 81 + 4 + 3 + 578 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 7096896 + 74338884 = 2664^2 + 8622^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 26062 + ... + 29018.

Almost surely, 2^81435780 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 81435780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (135293004).

81435780 is an abundant number, since it is smaller than the sum of its proper divisors (189150228).

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

81435780 is a wasteful number, since it uses less digits than its factorization.

81435780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2995 (or 2984 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 36.

The square root of 81435780 is about 9024.1775248496. The cubic root of 81435780 is about 433.4494140036.

It can be divided in two parts, 81435 and 780, that added together give a triangular number (82215 = T₄₀₅).

The spelling of 81435780 in words is "eighty-one million, four hundred thirty-five thousand, seven hundred eighty".