21513015 has 12 divisors (see below), whose sum is σ = 37289304. Its totient is φ = 11473584.

The previous prime is 21513013. The next prime is 21513031. The reversal of 21513015 is 51031512.

It is not a de Polignac number, because 21513015 - 2¹ = 21513013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 238989 + ... + 239078.

It is an arithmetic number, because the mean of its divisors is an integer number (3107442).

Almost surely, 2^21513015 is an apocalyptic number.

21513015 is a deficient number, since it is larger than the sum of its proper divisors (15776289).

21513015 is a wasteful number, since it uses less digits than its factorization.

21513015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 478078 (or 478075 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 18.

The square root of 21513015 is about 4638.2124789621. The cubic root of 21513015 is about 278.1209857604.

Adding to 21513015 its reverse (51031512), we get a palindrome (72544527).

The spelling of 21513015 in words is "twenty-one million, five hundred thirteen thousand, fifteen".