21252811 has 4 divisors (see below), whose sum is σ = 22371400. Its totient is φ = 20134224.

The previous prime is 21252809. The next prime is 21252821. The reversal of 21252811 is 11825212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21252811 - 2¹ = 21252809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21252821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 559266 + ... + 559303.

It is an arithmetic number, because the mean of its divisors is an integer number (5592850).

Almost surely, 2^21252811 is an apocalyptic number.

21252811 is a deficient number, since it is larger than the sum of its proper divisors (1118589).

21252811 is a wasteful number, since it uses less digits than its factorization.

21252811 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1118588.

The product of its digits is 320, while the sum is 22.

The square root of 21252811 is about 4610.0771143225. The cubic root of 21252811 is about 276.9951256164.

The spelling of 21252811 in words is "twenty-one million, two hundred fifty-two thousand, eight hundred eleven".