21418091 has 4 divisors (see below), whose sum is σ = 21737832. Its totient is φ = 21098352.

The previous prime is 21418087. The next prime is 21418099. The reversal of 21418091 is 19081412.

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 21418091 - 2² = 21418087 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21418091.

It is not an unprimeable number, because it can be changed into a prime (21418099) 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, 159770 + ... + 159903.

It is an arithmetic number, because the mean of its divisors is an integer number (5434458).

Almost surely, 2^21418091 is an apocalyptic number.

21418091 is a deficient number, since it is larger than the sum of its proper divisors (319741).

21418091 is an equidigital number, since it uses as much as digits as its factorization.

21418091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319740.

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 21418091 is about 4627.9683447491. The cubic root of 21418091 is about 277.7113224077.

The spelling of 21418091 in words is "twenty-one million, four hundred eighteen thousand, ninety-one".