21981783 has 4 divisors (see below), whose sum is σ = 29309048. Its totient is φ = 14654520.

The previous prime is 21981763. The next prime is 21981793. The reversal of 21981783 is 38718912.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21981783 - 2¹³ = 21973591 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 (21981733) 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, 3663628 + ... + 3663633.

It is an arithmetic number, because the mean of its divisors is an integer number (7327262).

Almost surely, 2^21981783 is an apocalyptic number.

21981783 is a deficient number, since it is larger than the sum of its proper divisors (7327265).

21981783 is an equidigital number, since it uses as much as digits as its factorization.

21981783 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7327264.

The product of its digits is 24192, while the sum is 39.

The square root of 21981783 is about 4688.4734189286. The cubic root of 21981783 is about 280.1265711775.

The spelling of 21981783 in words is "twenty-one million, nine hundred eighty-one thousand, seven hundred eighty-three".