21055705 has 16 divisors (see below), whose sum is σ = 29016000. Its totient is φ = 14506560.

The previous prime is 21055703. The next prime is 21055717. The reversal of 21055705 is 50755012.

It is a happy number.

It is not a de Polignac number, because 21055705 - 2¹ = 21055703 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21055705.

It is not an unprimeable number, because it can be changed into a prime (21055703) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9030 + ... + 11119.

It is an arithmetic number, because the mean of its divisors is an integer number (1813500).

Almost surely, 2^21055705 is an apocalyptic number.

It is an amenable number.

21055705 is a deficient number, since it is larger than the sum of its proper divisors (7960295).

21055705 is a wasteful number, since it uses less digits than its factorization.

21055705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20184.

The product of its (nonzero) digits is 1750, while the sum is 25.

The square root of 21055705 is about 4588.6495834831. The cubic root of 21055705 is about 276.1361480843.

The spelling of 21055705 in words is "twenty-one million, fifty-five thousand, seven hundred five".