81243405 has 56 divisors (see below), whose sum is σ = 151096320. Its totient is φ = 41873760.

The previous prime is 81243403. The next prime is 81243419. The reversal of 81243405 is 50434218.

It is not a de Polignac number, because 81243405 - 2¹ = 81243403 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81243403) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 112636 + ... + 113354.

Almost surely, 2^81243405 is an apocalyptic number.

It is an amenable number.

81243405 is a deficient number, since it is larger than the sum of its proper divisors (69852915).

81243405 is an equidigital number, since it uses as much as digits as its factorization.

81243405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 773 (or 758 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 81243405 is about 9013.5123564568. The cubic root of 81243405 is about 433.1078336931.

The spelling of 81243405 in words is "eighty-one million, two hundred forty-three thousand, four hundred five".