21554855 has 24 divisors (see below), whose sum is σ = 30432528. Its totient is φ = 14611968.

The previous prime is 21554849. The next prime is 21554881. The reversal of 21554855 is 55845512.

It is not a de Polignac number, because 21554855 - 2⁴ = 21554839 is a prime.

It is a super-2 number, since 2×21554855² = 929223548142050, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 23312 + ... + 24218.

It is an arithmetic number, because the mean of its divisors is an integer number (1268022).

Almost surely, 2^21554855 is an apocalyptic number.

21554855 is a deficient number, since it is larger than the sum of its proper divisors (8877673).

21554855 is an equidigital number, since it uses as much as digits as its factorization.

21554855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1023 (or 1016 counting only the distinct ones).

The product of its digits is 40000, while the sum is 35.

The square root of 21554855 is about 4642.7206463452. The cubic root of 21554855 is about 278.3011719764.

The spelling of 21554855 in words is "twenty-one million, five hundred fifty-four thousand, eight hundred fifty-five".