21305955 has 16 divisors (see below), whose sum is σ = 37188864. Its totient is φ = 10330080.

The previous prime is 21305939. The next prime is 21305983. The reversal of 21305955 is 55950312.

It is not a de Polignac number, because 21305955 - 2⁴ = 21305939 is a prime.

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, 64399 + ... + 64728.

It is an arithmetic number, because the mean of its divisors is an integer number (2324304).

Almost surely, 2^21305955 is an apocalyptic number.

21305955 is a deficient number, since it is larger than the sum of its proper divisors (15882909).

21305955 is a wasteful number, since it uses less digits than its factorization.

21305955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129146.

The product of its (nonzero) digits is 6750, while the sum is 30.

The square root of 21305955 is about 4615.8374104814. The cubic root of 21305955 is about 277.2258147241.

The spelling of 21305955 in words is "twenty-one million, three hundred five thousand, nine hundred fifty-five".