21265251 has 8 divisors (see below), whose sum is σ = 32404224. Its totient is φ = 12151560.

The previous prime is 21265241. The next prime is 21265253. The reversal of 21265251 is 15256212.

It is a happy number.

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

It is not a de Polignac number, because 21265251 - 2⁵ = 21265219 is a prime.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21265253) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 506295 + ... + 506336.

It is an arithmetic number, because the mean of its divisors is an integer number (4050528).

Almost surely, 2^21265251 is an apocalyptic number.

21265251 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21265251 is a deficient number, since it is larger than the sum of its proper divisors (11138973).

21265251 is a wasteful number, since it uses less digits than its factorization.

21265251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1012641.

The product of its digits is 1200, while the sum is 24.

The square root of 21265251 is about 4611.4261351560. The cubic root of 21265251 is about 277.0491599943.

The spelling of 21265251 in words is "twenty-one million, two hundred sixty-five thousand, two hundred fifty-one".