81561383 has 4 divisors (see below), whose sum is σ = 82402320. Its totient is φ = 80720448.

The previous prime is 81561373. The next prime is 81561391. The reversal of 81561383 is 38316518.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 38316518 = 2 ⋅19158259.

It is a cyclic number.

It is not a de Polignac number, because 81561383 - 2⁸ = 81561127 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561323) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 420323 + ... + 420516.

It is an arithmetic number, because the mean of its divisors is an integer number (20600580).

Almost surely, 2^81561383 is an apocalyptic number.

81561383 is a deficient number, since it is larger than the sum of its proper divisors (840937).

81561383 is an equidigital number, since it uses as much as digits as its factorization.

81561383 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 840936.

The product of its digits is 17280, while the sum is 35.

The square root of 81561383 is about 9031.1340926818. The cubic root of 81561383 is about 433.6721440320.

The spelling of 81561383 in words is "eighty-one million, five hundred sixty-one thousand, three hundred eighty-three".