81440385 has 16 divisors (see below), whose sum is σ = 140328384. Its totient is φ = 40093632.

The previous prime is 81440377. The next prime is 81440393. The reversal of 81440385 is 58304418.

It is an interprime number because it is at equal distance from previous prime (81440377) and next prime (81440393).

It is not a de Polignac number, because 81440385 - 2³ = 81440377 is a prime.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 208627 + ... + 209016.

It is an arithmetic number, because the mean of its divisors is an integer number (8770524).

Almost surely, 2^81440385 is an apocalyptic number.

It is an amenable number.

81440385 is a deficient number, since it is larger than the sum of its proper divisors (58887999).

81440385 is a wasteful number, since it uses less digits than its factorization.

81440385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 417664.

The product of its (nonzero) digits is 15360, while the sum is 33.

The square root of 81440385 is about 9024.4326691488. The cubic root of 81440385 is about 433.4575840280.

The spelling of 81440385 in words is "eighty-one million, four hundred forty thousand, three hundred eighty-five".