81561010 has 16 divisors (see below), whose sum is σ = 149299200. Its totient is φ = 32071216.

The previous prime is 81560971. The next prime is 81561017. The reversal of 81561010 is 1016518.

It is not an unprimeable number, because it can be changed into a prime (81561017) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 68530 + ... + 69709.

It is an arithmetic number, because the mean of its divisors is an integer number (9331200).

Almost surely, 2^81561010 is an apocalyptic number.

81561010 is a deficient number, since it is larger than the sum of its proper divisors (67738190).

81561010 is a wasteful number, since it uses less digits than its factorization.

81561010 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138305.

The product of its (nonzero) digits is 240, while the sum is 22.

The square root of 81561010 is about 9031.1134418742. The cubic root of 81561010 is about 433.6714829350.

Adding to 81561010 its reverse (1016518), we get a palindrome (82577528).

The spelling of 81561010 in words is "eighty-one million, five hundred sixty-one thousand, ten".