21555275 has 24 divisors (see below), whose sum is σ = 31381920. Its totient is φ = 14376960.

The previous prime is 21555271. The next prime is 21555277. The reversal of 21555275 is 57255512.

It is not a de Polignac number, because 21555275 - 2² = 21555271 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21555271) 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 23 ways as a sum of consecutive naturals, for example, 4811 + ... + 8139.

It is an arithmetic number, because the mean of its divisors is an integer number (1307580).

Almost surely, 2^21555275 is an apocalyptic number.

21555275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21555275 is a deficient number, since it is larger than the sum of its proper divisors (9826645).

21555275 is a wasteful number, since it uses less digits than its factorization.

21555275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3383 (or 3378 counting only the distinct ones).

The product of its digits is 17500, while the sum is 32.

The square root of 21555275 is about 4642.7658782239. The cubic root of 21555275 is about 278.3029795465.

The spelling of 21555275 in words is "twenty-one million, five hundred fifty-five thousand, two hundred seventy-five".