21709801 has 4 divisors (see below), whose sum is σ = 21734100. Its totient is φ = 21685504.

The previous prime is 21709781. The next prime is 21709813. The reversal of 21709801 is 10890712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1243225 + 20466576 = 1115^2 + 4524^2 .

It is a cyclic number.

It is not a de Polignac number, because 21709801 - 2¹³ = 21701609 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 21709801.

It is not an unprimeable number, because it can be changed into a prime (21709841) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 10756 + ... + 12613.

It is an arithmetic number, because the mean of its divisors is an integer number (5433525).

Almost surely, 2^21709801 is an apocalyptic number.

It is an amenable number.

21709801 is a deficient number, since it is larger than the sum of its proper divisors (24299).

21709801 is an equidigital number, since it uses as much as digits as its factorization.

21709801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24298.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21709801 is about 4659.3777481548. The cubic root of 21709801 is about 278.9664318157.

The spelling of 21709801 in words is "twenty-one million, seven hundred nine thousand, eight hundred one".