221998987 has 4 divisors (see below), whose sum is σ = 253713136. Its totient is φ = 190284840.

The previous prime is 221998957. The next prime is 221998993. The reversal of 221998987 is 789899122.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 221998987 - 2¹¹ = 221996939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221998957) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15857064 + ... + 15857077.

It is an arithmetic number, because the mean of its divisors is an integer number (63428284).

Almost surely, 2^221998987 is an apocalyptic number.

221998987 is a deficient number, since it is larger than the sum of its proper divisors (31714149).

221998987 is an equidigital number, since it uses as much as digits as its factorization.

221998987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31714148.

The product of its digits is 1306368, while the sum is 55.

The square root of 221998987 is about 14899.6304316584. The cubic root of 221998987 is about 605.5039736640.

The spelling of 221998987 in words is "two hundred twenty-one million, nine hundred ninety-eight thousand, nine hundred eighty-seven".