21513005 has 4 divisors (see below), whose sum is σ = 25815612. Its totient is φ = 17210400.

The previous prime is 21513001. The next prime is 21513013. The reversal of 21513005 is 50031512.

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 8219689 + 13293316 = 2867^2 + 3646^2 .

It is not a de Polignac number, because 21513005 - 2² = 21513001 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 (21513001) 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, 2151296 + ... + 2151305.

It is an arithmetic number, because the mean of its divisors is an integer number (6453903).

Almost surely, 2^21513005 is an apocalyptic number.

It is an amenable number.

21513005 is a deficient number, since it is larger than the sum of its proper divisors (4302607).

21513005 is an equidigital number, since it uses as much as digits as its factorization.

21513005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4302606.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21513005 is about 4638.2114009605. The cubic root of 21513005 is about 278.1209426669.

Adding to 21513005 its reverse (50031512), we get a palindrome (71544517).

The spelling of 21513005 in words is "twenty-one million, five hundred thirteen thousand, five".