21501313 has 4 divisors (see below), whose sum is σ = 21513940. Its totient is φ = 21488688.

The previous prime is 21501299. The next prime is 21501323. The reversal of 21501313 is 31310512.

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 11716929 + 9784384 = 3423^2 + 3128^2 .

It is a cyclic number.

It is not a de Polignac number, because 21501313 - 2⁵ = 21501281 is a prime.

It is a super-4 number, since 4×21501313⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21501323) 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, 3270 + ... + 7327.

It is an arithmetic number, because the mean of its divisors is an integer number (5378485).

Almost surely, 2^21501313 is an apocalyptic number.

It is an amenable number.

21501313 is a deficient number, since it is larger than the sum of its proper divisors (12627).

21501313 is a wasteful number, since it uses less digits than its factorization.

21501313 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12626.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21501313 is about 4636.9508300175. The cubic root of 21501313 is about 278.0705486635.

Adding to 21501313 its reverse (31310512), we get a palindrome (52811825).

The spelling of 21501313 in words is "twenty-one million, five hundred one thousand, three hundred thirteen".