21245791 has 4 divisors (see below), whose sum is σ = 24280912. Its totient is φ = 18210672.

The previous prime is 21245779. The next prime is 21245797. The reversal of 21245791 is 19754212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21245791 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 (21245797) 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, 1517550 + ... + 1517563.

It is an arithmetic number, because the mean of its divisors is an integer number (6070228).

Almost surely, 2^21245791 is an apocalyptic number.

21245791 is a deficient number, since it is larger than the sum of its proper divisors (3035121).

21245791 is an equidigital number, since it uses as much as digits as its factorization.

21245791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3035120.

The product of its digits is 5040, while the sum is 31.

The square root of 21245791 is about 4609.3156758894. The cubic root of 21245791 is about 276.9646242407.

The spelling of 21245791 in words is "twenty-one million, two hundred forty-five thousand, seven hundred ninety-one".