21282491 has 4 divisors (see below), whose sum is σ = 22016400. Its totient is φ = 20548584.

The previous prime is 21282467. The next prime is 21282497. The reversal of 21282491 is 19428212.

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-21282491 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29), and also a Moran number because the ratio is a prime number: 733879 = 21282491 / (2 + 1 + 2 + 8 + 2 + 4 + 9 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21282497) 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, 366911 + ... + 366968.

It is an arithmetic number, because the mean of its divisors is an integer number (5504100).

Almost surely, 2^21282491 is an apocalyptic number.

21282491 is a deficient number, since it is larger than the sum of its proper divisors (733909).

21282491 is an equidigital number, since it uses as much as digits as its factorization.

21282491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 733908.

The product of its digits is 2304, while the sum is 29.

The square root of 21282491 is about 4613.2950263342. The cubic root of 21282491 is about 277.1240088225.

The spelling of 21282491 in words is "twenty-one million, two hundred eighty-two thousand, four hundred ninety-one".