21055571 has 8 divisors (see below), whose sum is σ = 22516704. Its totient is φ = 19619200.

The previous prime is 21055561. The next prime is 21055579. The reversal of 21055571 is 17555012.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21055571 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21055571.

It is not an unprimeable number, because it can be changed into a prime (21055579) 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, 4415 + ... + 7848.

It is an arithmetic number, because the mean of its divisors is an integer number (2814588).

Almost surely, 2^21055571 is an apocalyptic number.

21055571 is a deficient number, since it is larger than the sum of its proper divisors (1461133).

21055571 is a wasteful number, since it uses less digits than its factorization.

21055571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12381.

The product of its (nonzero) digits is 1750, while the sum is 26.

The square root of 21055571 is about 4588.6349822142. The cubic root of 21055571 is about 276.1355622998.

The spelling of 21055571 in words is "twenty-one million, fifty-five thousand, five hundred seventy-one".