21240207 has 6 divisors (see below), whose sum is σ = 30680312. Its totient is φ = 14160132.

The previous prime is 21240179. The next prime is 21240211. The reversal of 21240207 is 70204212.

It is not a de Polignac number, because 21240207 - 2¹⁴ = 21223823 is a prime.

It is a super-2 number, since 2×21240207² = 902292786805698, which contains 22 as substring.

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 21240207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21240907) 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, 1180003 + ... + 1180020.

Almost surely, 2^21240207 is an apocalyptic number.

21240207 is a deficient number, since it is larger than the sum of its proper divisors (9440105).

21240207 is a wasteful number, since it uses less digits than its factorization.

21240207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2360029 (or 2360026 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 21240207 is about 4608.7099062536. The cubic root of 21240207 is about 276.9403573796.

Adding to 21240207 its reverse (70204212), we get a palindrome (91444419).

The spelling of 21240207 in words is "twenty-one million, two hundred forty thousand, two hundred seven".