21020357 has 4 divisors (see below), whose sum is σ = 21029856. Its totient is φ = 21010860.

The previous prime is 21020353. The next prime is 21020369. The reversal of 21020357 is 75302012.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21020357 - 2² = 21020353 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 (21020353) 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, 518 + ... + 6504.

It is an arithmetic number, because the mean of its divisors is an integer number (5257464).

Almost surely, 2^21020357 is an apocalyptic number.

It is an amenable number.

21020357 is a deficient number, since it is larger than the sum of its proper divisors (9499).

21020357 is an equidigital number, since it uses as much as digits as its factorization.

21020357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9498.

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 21020357 is about 4584.7962877319. The cubic root of 21020357 is about 275.9815371323.

Adding to 21020357 its reverse (75302012), we get a palindrome (96322369).

The spelling of 21020357 in words is "twenty-one million, twenty thousand, three hundred fifty-seven".