21126857 has 8 divisors (see below), whose sum is σ = 22349184. Its totient is φ = 19929888.

The previous prime is 21126851. The next prime is 21126887. The reversal of 21126857 is 75862112.

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

It is a cyclic number.

It is not a de Polignac number, because 21126857 - 2⁸ = 21126601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21126851) 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, 4613 + ... + 7970.

It is an arithmetic number, because the mean of its divisors is an integer number (2793648).

Almost surely, 2^21126857 is an apocalyptic number.

It is an amenable number.

21126857 is a deficient number, since it is larger than the sum of its proper divisors (1222327).

21126857 is a wasteful number, since it uses less digits than its factorization.

21126857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12679.

The product of its digits is 6720, while the sum is 32.

The square root of 21126857 is about 4596.3960882413. The cubic root of 21126857 is about 276.4468405924.

Adding to 21126857 its reverse (75862112), we get a palindrome (96988969).

The spelling of 21126857 in words is "twenty-one million, one hundred twenty-six thousand, eight hundred fifty-seven".