81047921 has 8 divisors (see below), whose sum is σ = 81681600. Its totient is φ = 80417232.

The previous prime is 81047867. The next prime is 81047927. The reversal of 81047921 is 12974018.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81047921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81047927) 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, 91346 + ... + 92228.

It is an arithmetic number, because the mean of its divisors is an integer number (10210200).

Almost surely, 2^81047921 is an apocalyptic number.

It is an amenable number.

81047921 is a deficient number, since it is larger than the sum of its proper divisors (633679).

81047921 is a wasteful number, since it uses less digits than its factorization.

81047921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1495.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 81047921 is about 9002.6618841318. The cubic root of 81047921 is about 432.7601802483.

The spelling of 81047921 in words is "eighty-one million, forty-seven thousand, nine hundred twenty-one".