21771855 has 32 divisors (see below), whose sum is σ = 44236800. Its totient is φ = 9952416.

The previous prime is 21771833. The next prime is 21771859. The reversal of 21771855 is 55817712.

It is not a de Polignac number, because 21771855 - 2⁶ = 21771791 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21771859) 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 31 ways as a sum of consecutive naturals, for example, 10575 + ... + 12464.

It is an arithmetic number, because the mean of its divisors is an integer number (1382400).

Almost surely, 2^21771855 is an apocalyptic number.

21771855 is an abundant number, since it is smaller than the sum of its proper divisors (22464945).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21771855 is a wasteful number, since it uses less digits than its factorization.

21771855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23060 (or 23054 counting only the distinct ones).

The product of its digits is 19600, while the sum is 36.

The square root of 21771855 is about 4666.0320401815. The cubic root of 21771855 is about 279.2319726428.

The spelling of 21771855 in words is "twenty-one million, seven hundred seventy-one thousand, eight hundred fifty-five".