21720301 has 4 divisors (see below), whose sum is σ = 22130172. Its totient is φ = 21310432.

The previous prime is 21720277. The next prime is 21720311. The reversal of 21720301 is 10302712.

It is a happy number.

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 6502500 + 15217801 = 2550^2 + 3901^2 .

It is a cyclic number.

It is not a de Polignac number, because 21720301 - 2¹³ = 21712109 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720311) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 204856 + ... + 204961.

It is an arithmetic number, because the mean of its divisors is an integer number (5532543).

Almost surely, 2^21720301 is an apocalyptic number.

It is an amenable number.

21720301 is a deficient number, since it is larger than the sum of its proper divisors (409871).

21720301 is an equidigital number, since it uses as much as digits as its factorization.

21720301 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 409870.

The product of its (nonzero) digits is 84, while the sum is 16.

The square root of 21720301 is about 4660.5043718465. The cubic root of 21720301 is about 279.0113988397.

The spelling of 21720301 in words is "twenty-one million, seven hundred twenty thousand, three hundred one".