21901998 has 8 divisors (see below), whose sum is σ = 43804008. Its totient is φ = 7300664.

The previous prime is 21901993. The next prime is 21902029. The reversal of 21901998 is 89910912.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

21901998 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21901993) 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, 1825161 + ... + 1825172.

It is an arithmetic number, because the mean of its divisors is an integer number (5475501).

Almost surely, 2^21901998 is an apocalyptic number.

21901998 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21901998 is a wasteful number, since it uses less digits than its factorization.

21901998 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3650338.

The product of its (nonzero) digits is 11664, while the sum is 39.

The square root of 21901998 is about 4679.9570510850. The cubic root of 21901998 is about 279.7872448437.

The spelling of 21901998 in words is "twenty-one million, nine hundred one thousand, nine hundred ninety-eight".