21256311 has 4 divisors (see below), whose sum is σ = 28341752. Its totient is φ = 14170872.

The previous prime is 21256309. The next prime is 21256321. The reversal of 21256311 is 11365212.

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

It is not a de Polignac number, because 21256311 - 2¹ = 21256309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21256321) 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, 3542716 + ... + 3542721.

It is an arithmetic number, because the mean of its divisors is an integer number (7085438).

Almost surely, 2^21256311 is an apocalyptic number.

21256311 is a deficient number, since it is larger than the sum of its proper divisors (7085441).

21256311 is an equidigital number, since it uses as much as digits as its factorization.

21256311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7085440.

The product of its digits is 360, while the sum is 21.

The square root of 21256311 is about 4610.4567018897. The cubic root of 21256311 is about 277.0103303458.

The spelling of 21256311 in words is "twenty-one million, two hundred fifty-six thousand, three hundred eleven".