21403491 has 4 divisors (see below), whose sum is σ = 28537992. Its totient is φ = 14268992.

The previous prime is 21403483. The next prime is 21403559. The reversal of 21403491 is 19430412.

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 21403491 - 2³ = 21403483 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21403441) 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, 3567246 + ... + 3567251.

It is an arithmetic number, because the mean of its divisors is an integer number (7134498).

Almost surely, 2^21403491 is an apocalyptic number.

21403491 is a deficient number, since it is larger than the sum of its proper divisors (7134501).

21403491 is an equidigital number, since it uses as much as digits as its factorization.

21403491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7134500.

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 21403491 is about 4626.3907098299. The cubic root of 21403491 is about 277.6482058746.

The spelling of 21403491 in words is "twenty-one million, four hundred three thousand, four hundred ninety-one".