21921205 has 8 divisors (see below), whose sum is σ = 27016632. Its totient is φ = 17062848.

The previous prime is 21921191. The next prime is 21921227. The reversal of 21921205 is 50212912.

It can be written as a sum of positive squares in 4 ways, for example, as 2056356 + 19864849 = 1434^2 + 4457^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21921205 - 2⁹ = 21920693 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59062 + ... + 59431.

It is an arithmetic number, because the mean of its divisors is an integer number (3377079).

Almost surely, 2^21921205 is an apocalyptic number.

It is an amenable number.

21921205 is a deficient number, since it is larger than the sum of its proper divisors (5095427).

21921205 is a wasteful number, since it uses less digits than its factorization.

21921205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118535.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 21921205 is about 4682.0086501415. The cubic root of 21921205 is about 279.8690076049.

The spelling of 21921205 in words is "twenty-one million, nine hundred twenty-one thousand, two hundred five".