21053855 has 32 divisors (see below), whose sum is σ = 27993600. Its totient is φ = 15148672.

The previous prime is 21053839. The next prime is 21053861. The reversal of 21053855 is 55835012.

It is not a de Polignac number, because 21053855 - 2⁴ = 21053839 is a prime.

It is a super-2 number, since 2×21053855² = 886529620722050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 196712 + ... + 196818.

It is an arithmetic number, because the mean of its divisors is an integer number (874800).

Almost surely, 2^21053855 is an apocalyptic number.

21053855 is a deficient number, since it is larger than the sum of its proper divisors (6939745).

21053855 is a wasteful number, since it uses less digits than its factorization.

21053855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 223.

The product of its (nonzero) digits is 6000, while the sum is 29.

The square root of 21053855 is about 4588.4479946928. The cubic root of 21053855 is about 276.1280605401.

Adding to 21053855 its reverse (55835012), we get a palindrome (76888867).

The spelling of 21053855 in words is "twenty-one million, fifty-three thousand, eight hundred fifty-five".