83555721 has 6 divisors (see below), whose sum is σ = 120691610. Its totient is φ = 55703808.

The previous prime is 83555701. The next prime is 83555737. The reversal of 83555721 is 12755538.

83555721 is a `hidden beast` number, since 83 + 5 + 5 + 572 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 44355600 + 39200121 = 6660^2 + 6261^2 .

It is not a de Polignac number, because 83555721 - 2⁹ = 83555209 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (83555701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4641976 + ... + 4641993.

Almost surely, 2^83555721 is an apocalyptic number.

It is an amenable number.

83555721 is a deficient number, since it is larger than the sum of its proper divisors (37135889).

83555721 is a wasteful number, since it uses less digits than its factorization.

83555721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9283975 (or 9283972 counting only the distinct ones).

The product of its digits is 42000, while the sum is 36.

The square root of 83555721 is about 9140.8818502374. The cubic root of 83555721 is about 437.1784342898.

The spelling of 83555721 in words is "eighty-three million, five hundred fifty-five thousand, seven hundred twenty-one".