21308783 has 4 divisors (see below), whose sum is σ = 21328008. Its totient is φ = 21289560.

The previous prime is 21308767. The next prime is 21308789. The reversal of 21308783 is 38780312.

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 21308783 - 2⁴ = 21308767 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308789) 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, 7841 + ... + 10202.

It is an arithmetic number, because the mean of its divisors is an integer number (5332002).

Almost surely, 2^21308783 is an apocalyptic number.

21308783 is a deficient number, since it is larger than the sum of its proper divisors (19225).

21308783 is a wasteful number, since it uses less digits than its factorization.

21308783 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19224.

The product of its (nonzero) digits is 8064, while the sum is 32.

The square root of 21308783 is about 4616.1437369302. The cubic root of 21308783 is about 277.2380798384.

The spelling of 21308783 in words is "twenty-one million, three hundred eight thousand, seven hundred eighty-three".