21504863 has 4 divisors (see below), whose sum is σ = 22246440. Its totient is φ = 20763288.

The previous prime is 21504841. The next prime is 21504871. The reversal of 21504863 is 36840512.

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 21504863 - 2⁶ = 21504799 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: 741547 = 21504863 / (2 + 1 + 5 + 0 + 4 + 8 + 6 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21504823) 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, 370745 + ... + 370802.

It is an arithmetic number, because the mean of its divisors is an integer number (5561610).

Almost surely, 2^21504863 is an apocalyptic number.

21504863 is a deficient number, since it is larger than the sum of its proper divisors (741577).

21504863 is an equidigital number, since it uses as much as digits as its factorization.

21504863 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 741576.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21504863 is about 4637.3336088748. Note that the first 3 decimals coincide. The cubic root of 21504863 is about 278.0858515449.

The spelling of 21504863 in words is "twenty-one million, five hundred four thousand, eight hundred sixty-three".