21001315 has 4 divisors (see below), whose sum is σ = 25201584. Its totient is φ = 16801048.

The previous prime is 21001247. The next prime is 21001319. The reversal of 21001315 is 51310012.

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 21001315 - 2⁷ = 21001187 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001295 and 21001304.

It is not an unprimeable number, because it can be changed into a prime (21001319) 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, 2100127 + ... + 2100136.

It is an arithmetic number, because the mean of its divisors is an integer number (6300396).

Almost surely, 2^21001315 is an apocalyptic number.

21001315 is a deficient number, since it is larger than the sum of its proper divisors (4200269).

21001315 is an equidigital number, since it uses as much as digits as its factorization.

21001315 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4200268.

The product of its (nonzero) digits is 30, while the sum is 13.

The square root of 21001315 is about 4582.7191709726. The cubic root of 21001315 is about 275.8981762247.

Adding to 21001315 its reverse (51310012), we get a palindrome (72311327).

It can be divided in two parts, 21001 and 315, that added together give a square (21316 = 146²).

The spelling of 21001315 in words is "twenty-one million, one thousand, three hundred fifteen".