21103257 has 8 divisors (see below), whose sum is σ = 32157376. Its totient is φ = 12058992.

The previous prime is 21103253. The next prime is 21103267. The reversal of 21103257 is 75230112.

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

It is not a de Polignac number, because 21103257 - 2² = 21103253 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1004917 = 21103257 / (2 + 1 + 1 + 0 + 3 + 2 + 5 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21103253) 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, 502438 + ... + 502479.

It is an arithmetic number, because the mean of its divisors is an integer number (4019672).

Almost surely, 2^21103257 is an apocalyptic number.

It is an amenable number.

21103257 is a deficient number, since it is larger than the sum of its proper divisors (11054119).

21103257 is a wasteful number, since it uses less digits than its factorization.

21103257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1004927.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21103257 is about 4593.8281421925. The cubic root of 21103257 is about 276.3438661929.

Adding to 21103257 its reverse (75230112), we get a palindrome (96333369).

The spelling of 21103257 in words is "twenty-one million, one hundred three thousand, two hundred fifty-seven".