21643771 has 8 divisors (see below), whose sum is σ = 22972464. Its totient is φ = 20321280.

The previous prime is 21643757. The next prime is 21643823. The reversal of 21643771 is 17734612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21643771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21646771) 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 7 ways as a sum of consecutive naturals, for example, 7051 + ... + 9643.

It is an arithmetic number, because the mean of its divisors is an integer number (2871558).

Almost surely, 2^21643771 is an apocalyptic number.

21643771 is a deficient number, since it is larger than the sum of its proper divisors (1328693).

21643771 is a wasteful number, since it uses less digits than its factorization.

21643771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3101.

The product of its digits is 7056, while the sum is 31.

The square root of 21643771 is about 4652.2866420718. The cubic root of 21643771 is about 278.6833206688.

The spelling of 21643771 in words is "twenty-one million, six hundred forty-three thousand, seven hundred seventy-one".