21840091 has 16 divisors (see below), whose sum is σ = 27143424. Its totient is φ = 17110944.

The previous prime is 21840083. The next prime is 21840109. The reversal of 21840091 is 19004812.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21840091 - 2³ = 21840083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21840061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8616 + ... + 10858.

It is an arithmetic number, because the mean of its divisors is an integer number (1696464).

Almost surely, 2^21840091 is an apocalyptic number.

21840091 is a deficient number, since it is larger than the sum of its proper divisors (5303333).

21840091 is a wasteful number, since it uses less digits than its factorization.

21840091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2370.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21840091 is about 4673.3383143102. The cubic root of 21840091 is about 279.5233855986.

The spelling of 21840091 in words is "twenty-one million, eight hundred forty thousand, ninety-one".