21305801 has 6 divisors (see below), whose sum is σ = 23418906. Its totient is φ = 19368800.

The previous prime is 21305789. The next prime is 21305839. The reversal of 21305801 is 10850312.

It can be written as a sum of positive squares in only one way, i.e., 20939776 + 366025 = 4576^2 + 605^2 .

It is not a de Polignac number, because 21305801 - 2⁶ = 21305737 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21305891) 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 5 ways as a sum of consecutive naturals, for example, 87920 + ... + 88161.

It is an arithmetic number, because the mean of its divisors is an integer number (3903151).

Almost surely, 2^21305801 is an apocalyptic number.

It is an amenable number.

21305801 is a deficient number, since it is larger than the sum of its proper divisors (2113105).

21305801 is a wasteful number, since it uses less digits than its factorization.

21305801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176103 (or 176092 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21305801 is about 4615.8207287545. The cubic root of 21305801 is about 277.2251467907.

The spelling of 21305801 in words is "twenty-one million, three hundred five thousand, eight hundred one".