21050257 has 4 divisors (see below), whose sum is σ = 21130560. Its totient is φ = 20969956.

The previous prime is 21050251. The next prime is 21050269. The reversal of 21050257 is 75205012.

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 a de Polignac number, because none of the positive numbers 2^k-21050257 is a prime.

It is a super-2 number, since 2×21050257² = 886226639532098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21050251) 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, 39757 + ... + 40282.

It is an arithmetic number, because the mean of its divisors is an integer number (5282640).

Almost surely, 2^21050257 is an apocalyptic number.

It is an amenable number.

21050257 is a deficient number, since it is larger than the sum of its proper divisors (80303).

21050257 is an equidigital number, since it uses as much as digits as its factorization.

21050257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80302.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21050257 is about 4588.0559063725. The cubic root of 21050257 is about 276.1123300027.

Adding to 21050257 its reverse (75205012), we get a palindrome (96255269).

The spelling of 21050257 in words is "twenty-one million, fifty thousand, two hundred fifty-seven".