21128783 has 8 divisors (see below), whose sum is σ = 22790208. Its totient is φ = 19472544.

The previous prime is 21128777. The next prime is 21128797. The reversal of 21128783 is 38782112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21128783 - 2⁶ = 21128719 is a prime.

It is a super-2 number, since 2×21128783² = 892850942122178, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21128083) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13466 + ... + 14952.

It is an arithmetic number, because the mean of its divisors is an integer number (2848776).

Almost surely, 2^21128783 is an apocalyptic number.

21128783 is a deficient number, since it is larger than the sum of its proper divisors (1661425).

21128783 is a wasteful number, since it uses less digits than its factorization.

21128783 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2593.

The product of its digits is 5376, while the sum is 32.

The square root of 21128783 is about 4596.6055954367. The cubic root of 21128783 is about 276.4552409654.

The spelling of 21128783 in words is "twenty-one million, one hundred twenty-eight thousand, seven hundred eighty-three".