21103251 has 16 divisors (see below), whose sum is σ = 30385824. Its totient is φ = 12950784.

The previous prime is 21103249. The next prime is 21103253. The reversal of 21103251 is 15230112.

It is an interprime number because it is at equal distance from previous prime (21103249) and next prime (21103253).

It is not a de Polignac number, because 21103251 - 2¹ = 21103249 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21103251.

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 15 ways as a sum of consecutive naturals, for example, 23625 + ... + 24501.

It is an arithmetic number, because the mean of its divisors is an integer number (1899114).

Almost surely, 2^21103251 is an apocalyptic number.

21103251 is a deficient number, since it is larger than the sum of its proper divisors (9282573).

21103251 is a wasteful number, since it uses less digits than its factorization.

21103251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1510.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21103251 is about 4593.8274891424. The cubic root of 21103251 is about 276.3438400033.

Adding to 21103251 its reverse (15230112), we get a palindrome (36333363).

The spelling of 21103251 in words is "twenty-one million, one hundred three thousand, two hundred fifty-one".