21548591 has 4 divisors (see below), whose sum is σ = 21790800. Its totient is φ = 21306384.

The previous prime is 21548587. The next prime is 21548621. The reversal of 21548591 is 19584512.

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 21548591 - 2² = 21548587 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21548531) 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, 120971 + ... + 121148.

It is an arithmetic number, because the mean of its divisors is an integer number (5447700).

Almost surely, 2^21548591 is an apocalyptic number.

21548591 is a deficient number, since it is larger than the sum of its proper divisors (242209).

21548591 is an equidigital number, since it uses as much as digits as its factorization.

21548591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242208.

The product of its digits is 14400, while the sum is 35.

The square root of 21548591 is about 4642.0459928786. The cubic root of 21548591 is about 278.2742105728.

The spelling of 21548591 in words is "twenty-one million, five hundred forty-eight thousand, five hundred ninety-one".