81421609 has 8 divisors (see below), whose sum is σ = 82415520. Its totient is φ = 80433600.

The previous prime is 81421579. The next prime is 81421649. The reversal of 81421609 is 90612418.

It is a happy number.

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 81421609 - 2⁵ = 81421577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81421649) 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, 30282 + ... + 32860.

It is an arithmetic number, because the mean of its divisors is an integer number (10301940).

Almost surely, 2^81421609 is an apocalyptic number.

It is an amenable number.

81421609 is a deficient number, since it is larger than the sum of its proper divisors (993911).

81421609 is a wasteful number, since it uses less digits than its factorization.

81421609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2951.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 81421609 is about 9023.3923221813. The cubic root of 81421609 is about 433.4242703957.

The spelling of 81421609 in words is "eighty-one million, four hundred twenty-one thousand, six hundred nine".