21548391 has 4 divisors (see below), whose sum is σ = 28731192. Its totient is φ = 14365592.

The previous prime is 21548389. The next prime is 21548399. The reversal of 21548391 is 19384512.

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 21548391 - 2¹ = 21548389 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21548399) 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, 3591396 + ... + 3591401.

It is an arithmetic number, because the mean of its divisors is an integer number (7182798).

Almost surely, 2^21548391 is an apocalyptic number.

21548391 is a deficient number, since it is larger than the sum of its proper divisors (7182801).

21548391 is an equidigital number, since it uses as much as digits as its factorization.

21548391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7182800.

The product of its digits is 8640, while the sum is 33.

The square root of 21548391 is about 4642.0244506034. The cubic root of 21548391 is about 278.2733496501.

The spelling of 21548391 in words is "twenty-one million, five hundred forty-eight thousand, three hundred ninety-one".