21371021 has 8 divisors (see below), whose sum is σ = 24478080. Its totient is φ = 18277488.

The previous prime is 21371011. The next prime is 21371027. The reversal of 21371021 is 12017312.

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-21371021 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 (21371027) 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, 275 + ... + 6543.

It is an arithmetic number, because the mean of its divisors is an integer number (3059760).

Almost surely, 2^21371021 is an apocalyptic number.

It is an amenable number.

21371021 is a deficient number, since it is larger than the sum of its proper divisors (3107059).

21371021 is an equidigital number, since it uses as much as digits as its factorization.

21371021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6763.

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21371021 is about 4622.8801628422. The cubic root of 21371021 is about 277.5077334641.

Adding to 21371021 its reverse (12017312), we get a palindrome (33388333).

The spelling of 21371021 in words is "twenty-one million, three hundred seventy-one thousand, twenty-one".