84180721 has 2 divisors, whose sum is σ = 84180722. Its totient is φ = 84180720.

The previous prime is 84180709. The next prime is 84180737. The reversal of 84180721 is 12708148.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73290721 + 10890000 = 8561^2 + 3300^2 .

It is a cyclic number.

It is not a de Polignac number, because 84180721 - 2⁵ = 84180689 is a prime.

It is not a weakly prime, because it can be changed into another prime (84180121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 42090360 + 42090361.

It is an arithmetic number, because the mean of its divisors is an integer number (42090361).

Almost surely, 2^84180721 is an apocalyptic number.

It is an amenable number.

84180721 is a deficient number, since it is larger than the sum of its proper divisors (1).

84180721 is an equidigital number, since it uses as much as digits as its factorization.

84180721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 84180721 is about 9175.0052316061. The cubic root of 84180721 is about 438.2657648439.

Adding to 84180721 its reverse (12708148), we get a palindrome (96888869).

The spelling of 84180721 in words is "eighty-four million, one hundred eighty thousand, seven hundred twenty-one".