21315155 has 8 divisors (see below), whose sum is σ = 25644384. Its totient is φ = 17008000.

The previous prime is 21315139. The next prime is 21315163. The reversal of 21315155 is 55151312.

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 21315155 - 2⁴ = 21315139 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21315155.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3311 + ... + 7320.

It is an arithmetic number, because the mean of its divisors is an integer number (3205548).

Almost surely, 2^21315155 is an apocalyptic number.

21315155 is a deficient number, since it is larger than the sum of its proper divisors (4329229).

21315155 is a wasteful number, since it uses less digits than its factorization.

21315155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11037.

The product of its digits is 750, while the sum is 23.

The square root of 21315155 is about 4616.8338718217. The cubic root of 21315155 is about 277.2657114021.

Adding to 21315155 its reverse (55151312), we get a palindrome (76466467).

The spelling of 21315155 in words is "twenty-one million, three hundred fifteen thousand, one hundred fifty-five".