21255515 has 16 divisors (see below), whose sum is σ = 26265600. Its totient is φ = 16504800.

The previous prime is 21255497. The next prime is 21255529. The reversal of 21255515 is 51555212.

It is not a de Polignac number, because 21255515 - 2¹⁰ = 21254491 is a prime.

It is a plaindrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35186 + ... + 35784.

It is an arithmetic number, because the mean of its divisors is an integer number (1641600).

Almost surely, 2^21255515 is an apocalyptic number.

21255515 is a deficient number, since it is larger than the sum of its proper divisors (5010085).

21255515 is a wasteful number, since it uses less digits than its factorization.

21255515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 802.

The product of its digits is 2500, while the sum is 26.

The square root of 21255515 is about 4610.3703755772. The cubic root of 21255515 is about 277.0068725026.

The spelling of 21255515 in words is "twenty-one million, two hundred fifty-five thousand, five hundred fifteen".