21264155 has 8 divisors (see below), whose sum is σ = 27836784. Its totient is φ = 15464800.

The previous prime is 21264151. The next prime is 21264157. The reversal of 21264155 is 55146212.

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

It is not a de Polignac number, because 21264155 - 2² = 21264151 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21264151) by changing a digit.

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, 193256 + ... + 193365.

It is an arithmetic number, because the mean of its divisors is an integer number (3479598).

Almost surely, 2^21264155 is an apocalyptic number.

21264155 is a deficient number, since it is larger than the sum of its proper divisors (6572629).

21264155 is a wasteful number, since it uses less digits than its factorization.

21264155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 386637.

The product of its digits is 2400, while the sum is 26.

The square root of 21264155 is about 4611.3072983700. The cubic root of 21264155 is about 277.0444002559.

The spelling of 21264155 in words is "twenty-one million, two hundred sixty-four thousand, one hundred fifty-five".