81097821 has 32 divisors (see below), whose sum is σ = 141031680. Its totient is φ = 45085248.

The previous prime is 81097811. The next prime is 81097823. The reversal of 81097821 is 12879018.

It is not a de Polignac number, because 81097821 - 2⁹ = 81097309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81097823) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1195 + ... + 12791.

It is an arithmetic number, because the mean of its divisors is an integer number (4407240).

Almost surely, 2^81097821 is an apocalyptic number.

It is an amenable number.

81097821 is a deficient number, since it is larger than the sum of its proper divisors (59933859).

81097821 is a wasteful number, since it uses less digits than its factorization.

81097821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11650 (or 11644 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 81097821 is about 9005.4328602239. The cubic root of 81097821 is about 432.8489766969.

It can be divided in two parts, 81097 and 821, that added together give a palindrome (81918).

The spelling of 81097821 in words is "eighty-one million, ninety-seven thousand, eight hundred twenty-one".