21207799 has 4 divisors (see below), whose sum is σ = 21348400. Its totient is φ = 21067200.

The previous prime is 21207793. The next prime is 21207811. The reversal of 21207799 is 99770212.

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 21207799 - 2¹⁵ = 21175031 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 (21207793) 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, 70074 + ... + 70375.

It is an arithmetic number, because the mean of its divisors is an integer number (5337100).

Almost surely, 2^21207799 is an apocalyptic number.

21207799 is a deficient number, since it is larger than the sum of its proper divisors (140601).

21207799 is a wasteful number, since it uses less digits than its factorization.

21207799 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140600.

The product of its (nonzero) digits is 15876, while the sum is 37.

The square root of 21207799 is about 4605.1926126928. The cubic root of 21207799 is about 276.7994351551.

It can be divided in two parts, 2 and 1207799, that added together give a square (1207801 = 1099²).

The spelling of 21207799 in words is "twenty-one million, two hundred seven thousand, seven hundred ninety-nine".