20721367 has 4 divisors (see below), whose sum is σ = 21622320. Its totient is φ = 19820416.

The previous prime is 20721353. The next prime is 20721373. The reversal of 20721367 is 76312702.

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

It is a cyclic number.

It is not a de Polignac number, because 20721367 - 2¹¹ = 20719319 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 (20721377) 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, 450442 + ... + 450487.

It is an arithmetic number, because the mean of its divisors is an integer number (5405580).

Almost surely, 2^20721367 is an apocalyptic number.

20721367 is a deficient number, since it is larger than the sum of its proper divisors (900953).

20721367 is an equidigital number, since it uses as much as digits as its factorization.

20721367 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 900952.

The product of its (nonzero) digits is 3528, while the sum is 28.

The square root of 20721367 is about 4552.0728245493. The cubic root of 20721367 is about 274.6667787635. Note that the first 3 decimals are identical.

The spelling of 20721367 in words is "twenty million, seven hundred twenty-one thousand, three hundred sixty-seven".