81896561 has 4 divisors (see below), whose sum is σ = 81933312. Its totient is φ = 81859812.

The previous prime is 81896539. The next prime is 81896567. The reversal of 81896561 is 16569818.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81896561 - 2¹⁰ = 81895537 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81896567) 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, 14801 + ... + 19566.

It is an arithmetic number, because the mean of its divisors is an integer number (20483328).

Almost surely, 2^81896561 is an apocalyptic number.

It is an amenable number.

81896561 is a deficient number, since it is larger than the sum of its proper divisors (36751).

81896561 is a wasteful number, since it uses less digits than its factorization.

81896561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36750.

The product of its digits is 103680, while the sum is 44.

The square root of 81896561 is about 9049.6718725045. The cubic root of 81896561 is about 434.2653933274.

It can be divided in two parts, 818 and 96561, that added together give a palindrome (97379).

The spelling of 81896561 in words is "eighty-one million, eight hundred ninety-six thousand, five hundred sixty-one".