21013555 has 8 divisors (see below), whose sum is σ = 25466544. Its totient is φ = 16644000.

The previous prime is 21013549. The next prime is 21013583. The reversal of 21013555 is 55531012.

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

It is not a de Polignac number, because 21013555 - 2⁷ = 21013427 is a prime.

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, 20301 + ... + 21310.

It is an arithmetic number, because the mean of its divisors is an integer number (3183318).

Almost surely, 2^21013555 is an apocalyptic number.

21013555 is a deficient number, since it is larger than the sum of its proper divisors (4452989).

21013555 is a wasteful number, since it uses less digits than its factorization.

21013555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41717.

The product of its (nonzero) digits is 750, while the sum is 22.

The square root of 21013555 is about 4584.0544281236. The cubic root of 21013555 is about 275.9517655330.

Adding to 21013555 its reverse (55531012), we get a palindrome (76544567).

The spelling of 21013555 in words is "twenty-one million, thirteen thousand, five hundred fifty-five".