21231207 has 16 divisors (see below), whose sum is σ = 32186880. Its totient is φ = 13824216.

The previous prime is 21231173. The next prime is 21231241. The reversal of 21231207 is 70213212.

It is an interprime number because it is at equal distance from previous prime (21231173) and next prime (21231241).

It is not a de Polignac number, because 21231207 - 2⁶ = 21231143 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21231207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231107) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7983 + ... + 10304.

It is an arithmetic number, because the mean of its divisors is an integer number (2011680).

Almost surely, 2^21231207 is an apocalyptic number.

21231207 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21231207 is a deficient number, since it is larger than the sum of its proper divisors (10955673).

21231207 is a wasteful number, since it uses less digits than its factorization.

21231207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18339 (or 18333 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21231207 is about 4607.7333907248. The cubic root of 21231207 is about 276.9012363651.

Adding to 21231207 its reverse (70213212), we get a palindrome (91444419).

The spelling of 21231207 in words is "twenty-one million, two hundred thirty-one thousand, two hundred seven".