21284857 has 4 divisors (see below), whose sum is σ = 23219856. Its totient is φ = 19349860.

The previous prime is 21284839. The next prime is 21284903. The reversal of 21284857 is 75848212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21284857 - 2²³ = 12896249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21282857) 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, 967483 + ... + 967504.

It is an arithmetic number, because the mean of its divisors is an integer number (5804964).

Almost surely, 2^21284857 is an apocalyptic number.

It is an amenable number.

21284857 is a deficient number, since it is larger than the sum of its proper divisors (1934999).

21284857 is a wasteful number, since it uses less digits than its factorization.

21284857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1934998.

The product of its digits is 35840, while the sum is 37.

The square root of 21284857 is about 4613.5514519728. The cubic root of 21284857 is about 277.1342778445.

The spelling of 21284857 in words is "twenty-one million, two hundred eighty-four thousand, eight hundred fifty-seven".