81405240 has 64 divisors (see below), whose sum is σ = 279106560. Its totient is φ = 18606720.

The previous prime is 81405229. The next prime is 81405301. The reversal of 81405240 is 4250418.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 81405240.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47616 + ... + 49295.

It is an arithmetic number, because the mean of its divisors is an integer number (4361040).

Almost surely, 2^81405240 is an apocalyptic number.

It is an amenable number.

81405240 is an abundant number, since it is smaller than the sum of its proper divisors (197701320).

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

81405240 is a wasteful number, since it uses less digits than its factorization.

81405240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96932 (or 96928 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 24.

The square root of 81405240 is about 9022.4852452082. The cubic root of 81405240 is about 433.3952232444.

Adding to 81405240 its reverse (4250418), we get a palindrome (85655658).

The spelling of 81405240 in words is "eighty-one million, four hundred five thousand, two hundred forty".