21438555 has 16 divisors (see below), whose sum is σ = 36107520. Its totient is φ = 10831968.

The previous prime is 21438541. The next prime is 21438589. The reversal of 21438555 is 55583412.

It is not a de Polignac number, because 21438555 - 2⁷ = 21438427 is a prime.

It is a super-2 number, since 2×21438555² = 919223280976050, which contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 37327 + ... + 37896.

It is an arithmetic number, because the mean of its divisors is an integer number (2256720).

Almost surely, 2^21438555 is an apocalyptic number.

21438555 is a deficient number, since it is larger than the sum of its proper divisors (14668965).

21438555 is a wasteful number, since it uses less digits than its factorization.

21438555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 75250.

The product of its digits is 24000, while the sum is 33.

The square root of 21438555 is about 4630.1787222525. The cubic root of 21438555 is about 277.7997410486.

The spelling of 21438555 in words is "twenty-one million, four hundred thirty-eight thousand, five hundred fifty-five".