21315311 has 4 divisors (see below), whose sum is σ = 21456624. Its totient is φ = 21174000.

The previous prime is 21315289. The next prime is 21315341. The reversal of 21315311 is 11351312.

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 21315311 - 2⁶ = 21315247 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21315311.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315341) 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, 70430 + ... + 70731.

It is an arithmetic number, because the mean of its divisors is an integer number (5364156).

Almost surely, 2^21315311 is an apocalyptic number.

21315311 is a deficient number, since it is larger than the sum of its proper divisors (141313).

21315311 is a wasteful number, since it uses less digits than its factorization.

21315311 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141312.

The product of its digits is 90, while the sum is 17.

The square root of 21315311 is about 4616.8507664857. The cubic root of 21315311 is about 277.2663878120.

Adding to 21315311 its reverse (11351312), we get a palindrome (32666623).

The spelling of 21315311 in words is "twenty-one million, three hundred fifteen thousand, three hundred eleven".