21389555 has 8 divisors (see below), whose sum is σ = 28000944. Its totient is φ = 15556000.

The previous prime is 21389521. The next prime is 21389561. The reversal of 21389555 is 55598312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21389555 - 2¹² = 21385459 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 194396 + ... + 194505.

It is an arithmetic number, because the mean of its divisors is an integer number (3500118).

Almost surely, 2^21389555 is an apocalyptic number.

21389555 is a deficient number, since it is larger than the sum of its proper divisors (6611389).

21389555 is a wasteful number, since it uses less digits than its factorization.

21389555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 388917.

The product of its digits is 54000, while the sum is 38.

The square root of 21389555 is about 4624.8843228777. The cubic root of 21389555 is about 277.5879330671.

The spelling of 21389555 in words is "twenty-one million, three hundred eighty-nine thousand, five hundred fifty-five".