21489091 has 4 divisors (see below), whose sum is σ = 23142112. Its totient is φ = 19836072.

The previous prime is 21489077. The next prime is 21489101. The reversal of 21489091 is 19098412.

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 21489091 - 2⁷ = 21488963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21489001) 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, 826491 + ... + 826516.

It is an arithmetic number, because the mean of its divisors is an integer number (5785528).

Almost surely, 2^21489091 is an apocalyptic number.

21489091 is a deficient number, since it is larger than the sum of its proper divisors (1653021).

21489091 is a wasteful number, since it uses less digits than its factorization.

21489091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1653020.

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 21489091 is about 4635.6327507688. The cubic root of 21489091 is about 278.0178507593.

The spelling of 21489091 in words is "twenty-one million, four hundred eighty-nine thousand, ninety-one".