81745621 has 8 divisors (see below), whose sum is σ = 84137760. Its totient is φ = 79387152.

The previous prime is 81745607. The next prime is 81745633. The reversal of 81745621 is 12654718.

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

It is a cyclic number.

It is not a de Polignac number, because 81745621 - 2⁷ = 81745493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81755621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3450 + ... + 13243.

It is an arithmetic number, because the mean of its divisors is an integer number (10517220).

Almost surely, 2^81745621 is an apocalyptic number.

It is an amenable number.

81745621 is a deficient number, since it is larger than the sum of its proper divisors (2392139).

81745621 is a wasteful number, since it uses less digits than its factorization.

81745621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16835.

The product of its digits is 13440, while the sum is 34.

The square root of 81745621 is about 9041.3284975163. The cubic root of 81745621 is about 433.9984373506.

The spelling of 81745621 in words is "eighty-one million, seven hundred forty-five thousand, six hundred twenty-one".