21253811 has 4 divisors (see below), whose sum is σ = 21302232. Its totient is φ = 21205392.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253811 is 11835212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21253811 - 2¹⁰ = 21252787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253861) 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, 23546 + ... + 24431.

It is an arithmetic number, because the mean of its divisors is an integer number (5325558).

Almost surely, 2^21253811 is an apocalyptic number.

21253811 is a deficient number, since it is larger than the sum of its proper divisors (48421).

21253811 is an equidigital number, since it uses as much as digits as its factorization.

21253811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48420.

The product of its digits is 480, while the sum is 23.

The square root of 21253811 is about 4610.1855711023. The cubic root of 21253811 is about 276.9994699951. Note that the first 3 decimals are identical.

The spelling of 21253811 in words is "twenty-one million, two hundred fifty-three thousand, eight hundred eleven".