81579561 has 48 divisors (see below), whose sum is σ = 132871104. Its totient is φ = 44343936.

The previous prime is 81579539. The next prime is 81579571. The reversal of 81579561 is 16597518.

It is not a de Polignac number, because 81579561 - 2⁵ = 81579529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81579571) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 288126 + ... + 288408.

It is an arithmetic number, because the mean of its divisors is an integer number (2768148).

Almost surely, 2^81579561 is an apocalyptic number.

It is an amenable number.

81579561 is a deficient number, since it is larger than the sum of its proper divisors (51291543).

81579561 is a wasteful number, since it uses less digits than its factorization.

81579561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 390 (or 383 counting only the distinct ones).

The product of its digits is 75600, while the sum is 42.

The square root of 81579561 is about 9032.1404439922. The cubic root of 81579561 is about 433.7043598771.

The spelling of 81579561 in words is "eighty-one million, five hundred seventy-nine thousand, five hundred sixty-one".