21989121 has 16 divisors (see below), whose sum is σ = 36553728. Its totient is φ = 11422800.

The previous prime is 21989119. The next prime is 21989129. The reversal of 21989121 is 12198912.

It is not a de Polignac number, because 21989121 - 2¹ = 21989119 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21989129) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47365 + ... + 47826.

It is an arithmetic number, because the mean of its divisors is an integer number (2284608).

Almost surely, 2^21989121 is an apocalyptic number.

21989121 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21989121 is a deficient number, since it is larger than the sum of its proper divisors (14564607).

21989121 is a wasteful number, since it uses less digits than its factorization.

21989121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95212.

The product of its digits is 2592, while the sum is 33.

The square root of 21989121 is about 4689.2559111228. The cubic root of 21989121 is about 280.1577385020.

It can be divided in two parts, 219891 and 21, that added together give a palindrome (219912).

The spelling of 21989121 in words is "twenty-one million, nine hundred eighty-nine thousand, one hundred twenty-one".