81969121 has 16 divisors (see below), whose sum is σ = 93795408. Its totient is φ = 70963200.

The previous prime is 81969119. The next prime is 81969143. The reversal of 81969121 is 12196918.

It can be written as a sum of positive squares in 8 ways, for example, as 24800400 + 57168721 = 4980^2 + 7561^2 .

It is a cyclic number.

It is not a de Polignac number, because 81969121 - 2¹ = 81969119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81966121) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 92601 + ... + 93481.

It is an arithmetic number, because the mean of its divisors is an integer number (5862213).

Almost surely, 2^81969121 is an apocalyptic number.

It is an amenable number.

81969121 is a deficient number, since it is larger than the sum of its proper divisors (11826287).

81969121 is a wasteful number, since it uses less digits than its factorization.

81969121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1332.

The product of its digits is 7776, while the sum is 37.

The square root of 81969121 is about 9053.6799700453. The cubic root of 81969121 is about 434.3936078912.

The spelling of 81969121 in words is "eighty-one million, nine hundred sixty-nine thousand, one hundred twenty-one".