21345491 has 4 divisors (see below), whose sum is σ = 21439752. Its totient is φ = 21251232.

The previous prime is 21345487. The next prime is 21345503. The reversal of 21345491 is 19454312.

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 21345491 - 2² = 21345487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21345431) 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, 46790 + ... + 47243.

It is an arithmetic number, because the mean of its divisors is an integer number (5359938).

Almost surely, 2^21345491 is an apocalyptic number.

21345491 is a deficient number, since it is larger than the sum of its proper divisors (94261).

21345491 is an equidigital number, since it uses as much as digits as its factorization.

21345491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94260.

The product of its digits is 4320, while the sum is 29.

The square root of 21345491 is about 4620.1180720843. The cubic root of 21345491 is about 277.3971850805.

The spelling of 21345491 in words is "twenty-one million, three hundred forty-five thousand, four hundred ninety-one".