21309475 has 12 divisors (see below), whose sum is σ = 28826280. Its totient is φ = 15497600.

The previous prime is 21309437. The next prime is 21309487. The reversal of 21309475 is 57490312.

It is not a de Polignac number, because 21309475 - 2¹⁹ = 20785187 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 38470 + ... + 39019.

It is an arithmetic number, because the mean of its divisors is an integer number (2402190).

Almost surely, 2^21309475 is an apocalyptic number.

21309475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21309475 is a deficient number, since it is larger than the sum of its proper divisors (7516805).

21309475 is a wasteful number, since it uses less digits than its factorization.

21309475 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77510 (or 77505 counting only the distinct ones).

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 21309475 is about 4616.2186906601. The cubic root of 21309475 is about 277.2410808963.

Adding to 21309475 its reverse (57490312), we get a palindrome (78799787).

The spelling of 21309475 in words is "twenty-one million, three hundred nine thousand, four hundred seventy-five".