21555885 has 16 divisors (see below), whose sum is σ = 37142784. Its totient is φ = 10612032.

The previous prime is 21555883. The next prime is 21555887. The reversal of 21555885 is 58855512.

It is an interprime number because it is at equal distance from previous prime (21555883) and next prime (21555887).

It is not a de Polignac number, because 21555885 - 2¹ = 21555883 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555883) 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 15 ways as a sum of consecutive naturals, for example, 55077 + ... + 55466.

It is an arithmetic number, because the mean of its divisors is an integer number (2321424).

Almost surely, 2^21555885 is an apocalyptic number.

It is an amenable number.

21555885 is a deficient number, since it is larger than the sum of its proper divisors (15586899).

21555885 is a wasteful number, since it uses less digits than its factorization.

21555885 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110564.

The product of its digits is 80000, while the sum is 39.

The square root of 21555885 is about 4642.8315713582. The cubic root of 21555885 is about 278.3056047851.

The spelling of 21555885 in words is "twenty-one million, five hundred fifty-five thousand, eight hundred eighty-five".