21275709 has 16 divisors (see below), whose sum is σ = 34914432. Its totient is φ = 11222208.

The previous prime is 21275707. The next prime is 21275711. The reversal of 21275709 is 90757212.

It is an interprime number because it is at equal distance from previous prime (21275707) and next prime (21275711).

It is not a de Polignac number, because 21275709 - 2¹ = 21275707 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21275709.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21275707) 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, 38694 + ... + 39239.

It is an arithmetic number, because the mean of its divisors is an integer number (2182152).

Almost surely, 2^21275709 is an apocalyptic number.

It is an amenable number.

21275709 is a deficient number, since it is larger than the sum of its proper divisors (13638723).

21275709 is a wasteful number, since it uses less digits than its factorization.

21275709 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77956.

The product of its (nonzero) digits is 8820, while the sum is 33.

The square root of 21275709 is about 4612.5599183100. The cubic root of 21275709 is about 277.0945690559.

The spelling of 21275709 in words is "twenty-one million, two hundred seventy-five thousand, seven hundred nine".