21024491 has 4 divisors (see below), whose sum is σ = 21040152. Its totient is φ = 21008832.

The previous prime is 21024467. The next prime is 21024499. The reversal of 21024491 is 19442012.

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-21024491 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21024499) 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, 5606 + ... + 8571.

It is an arithmetic number, because the mean of its divisors is an integer number (5260038).

Almost surely, 2^21024491 is an apocalyptic number.

21024491 is a deficient number, since it is larger than the sum of its proper divisors (15661).

21024491 is a wasteful number, since it uses less digits than its factorization.

21024491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15660.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21024491 is about 4585.2471034831. The cubic root of 21024491 is about 275.9996280538. Note that the first 3 decimals are identical.

The spelling of 21024491 in words is "twenty-one million, twenty-four thousand, four hundred ninety-one".