21173705 has 16 divisors (see below), whose sum is σ = 29113344. Its totient is φ = 14481600.

The previous prime is 21173701. The next prime is 21173717. The reversal of 21173705 is 50737112.

It is not a de Polignac number, because 21173705 - 2² = 21173701 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21173701) by changing a digit.

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, 24104 + ... + 24966.

It is an arithmetic number, because the mean of its divisors is an integer number (1819584).

Almost surely, 2^21173705 is an apocalyptic number.

It is an amenable number.

21173705 is a deficient number, since it is larger than the sum of its proper divisors (7939639).

21173705 is an equidigital number, since it uses as much as digits as its factorization.

21173705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1576.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 21173705 is about 4601.4894327815. The cubic root of 21173705 is about 276.6510265187.

The spelling of 21173705 in words is "twenty-one million, one hundred seventy-three thousand, seven hundred five".