21998147 has 4 divisors (see below), whose sum is σ = 22073520. Its totient is φ = 21922776.

The previous prime is 21998129. The next prime is 21998149. The reversal of 21998147 is 74189912.

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 21998147 - 2¹⁴ = 21981763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21998149) 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 3 ways as a sum of consecutive naturals, for example, 37247 + ... + 37832.

It is an arithmetic number, because the mean of its divisors is an integer number (5518380).

Almost surely, 2^21998147 is an apocalyptic number.

21998147 is a deficient number, since it is larger than the sum of its proper divisors (75373).

21998147 is an equidigital number, since it uses as much as digits as its factorization.

21998147 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75372.

The product of its digits is 36288, while the sum is 41.

The square root of 21998147 is about 4690.2182252002. The cubic root of 21998147 is about 280.1960659070.

The spelling of 21998147 in words is "twenty-one million, nine hundred ninety-eight thousand, one hundred forty-seven".