84561721 has 8 divisors (see below), whose sum is σ = 86776200. Its totient is φ = 82354560.

The previous prime is 84561703. The next prime is 84561727. The reversal of 84561721 is 12716548.

It can be written as a sum of positive squares in 4 ways, for example, as 1040400 + 83521321 = 1020^2 + 9139^2 .

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 84561721 - 2¹⁵ = 84528953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (84561727) 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, 27615 + ... + 30523.

It is an arithmetic number, because the mean of its divisors is an integer number (10847025).

Almost surely, 2^84561721 is an apocalyptic number.

It is an amenable number.

84561721 is a deficient number, since it is larger than the sum of its proper divisors (2214479).

84561721 is a wasteful number, since it uses less digits than its factorization.

84561721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3659.

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

The square root of 84561721 is about 9195.7447224246. The cubic root of 84561721 is about 438.9259634072.

The spelling of 84561721 in words is "eighty-four million, five hundred sixty-one thousand, seven hundred twenty-one".