21513255 has 8 divisors (see below), whose sum is σ = 34421232. Its totient is φ = 11473728.

The previous prime is 21513253. The next prime is 21513259. The reversal of 21513255 is 55231512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21513255 - 2¹ = 21513253 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 717094 + ... + 717123.

It is an arithmetic number, because the mean of its divisors is an integer number (4302654).

Almost surely, 2^21513255 is an apocalyptic number.

21513255 is a deficient number, since it is larger than the sum of its proper divisors (12907977).

21513255 is a wasteful number, since it uses less digits than its factorization.

21513255 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1434225.

The product of its digits is 1500, while the sum is 24.

The square root of 21513255 is about 4638.2383509259. The cubic root of 21513255 is about 278.1220199992.

Adding to 21513255 its reverse (55231512), we get a palindrome (76744767).

The spelling of 21513255 in words is "twenty-one million, five hundred thirteen thousand, two hundred fifty-five".