21709375 has 12 divisors (see below), whose sum is σ = 27138888. Its totient is φ = 17365000.

The previous prime is 21709349. The next prime is 21709399. The reversal of 21709375 is 57390712.

It is not a de Polignac number, because 21709375 - 2¹⁵ = 21676607 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21709375.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 349 + ... + 6598.

It is an arithmetic number, because the mean of its divisors is an integer number (2261574).

Almost surely, 2^21709375 is an apocalyptic number.

21709375 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21709375 is a deficient number, since it is larger than the sum of its proper divisors (5429513).

21709375 is an frugal number, since it uses more digits than its factorization.

21709375 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6972 (or 6952 counting only the distinct ones).

The product of its (nonzero) digits is 13230, while the sum is 34.

The square root of 21709375 is about 4659.3320336718. The cubic root of 21709375 is about 278.9646071332.

The spelling of 21709375 in words is "twenty-one million, seven hundred nine thousand, three hundred seventy-five".