21921207 has 24 divisors (see below), whose sum is σ = 36720768. Its totient is φ = 11386320.

The previous prime is 21921191. The next prime is 21921227. The reversal of 21921207 is 70212912.

It is not a de Polignac number, because 21921207 - 2⁴ = 21921191 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21921227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1773 + ... + 6854.

It is an arithmetic number, because the mean of its divisors is an integer number (1530032).

Almost surely, 2^21921207 is an apocalyptic number.

21921207 is a deficient number, since it is larger than the sum of its proper divisors (14799561).

21921207 is a wasteful number, since it uses less digits than its factorization.

21921207 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8659 (or 8648 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21921207 is about 4682.0088637251. The cubic root of 21921207 is about 279.8690161163.

The spelling of 21921207 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred seven".