21511313 has 4 divisors (see below), whose sum is σ = 21573300. Its totient is φ = 21449328.

The previous prime is 21511271. The next prime is 21511327. The reversal of 21511313 is 31311512.

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

It can be written as a sum of positive squares in 2 ways, for example, as 9560464 + 11950849 = 3092^2 + 3457^2 .

It is a cyclic number.

It is not a de Polignac number, because 21511313 - 2¹⁰ = 21510289 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21511291 and 21511300.

It is not an unprimeable number, because it can be changed into a prime (21511013) 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, 30470 + ... + 31167.

It is an arithmetic number, because the mean of its divisors is an integer number (5393325).

Almost surely, 2^21511313 is an apocalyptic number.

It is an amenable number.

21511313 is a deficient number, since it is larger than the sum of its proper divisors (61987).

21511313 is an equidigital number, since it uses as much as digits as its factorization.

21511313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61986.

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

The square root of 21511313 is about 4638.0289994781. The cubic root of 21511313 is about 278.1136510624.

Adding to 21511313 its reverse (31311512), we get a palindrome (52822825).

The spelling of 21511313 in words is "twenty-one million, five hundred eleven thousand, three hundred thirteen".