21909453 has 4 divisors (see below), whose sum is σ = 29212608. Its totient is φ = 14606300.

The previous prime is 21909449. The next prime is 21909463. The reversal of 21909453 is 35490912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21909453 - 2² = 21909449 is a prime.

It is a super-4 number, since 4×21909453⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909463) 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, 3651573 + ... + 3651578.

It is an arithmetic number, because the mean of its divisors is an integer number (7303152).

Almost surely, 2^21909453 is an apocalyptic number.

It is an amenable number.

21909453 is a deficient number, since it is larger than the sum of its proper divisors (7303155).

21909453 is an equidigital number, since it uses as much as digits as its factorization.

21909453 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7303154.

The product of its (nonzero) digits is 9720, while the sum is 33.

The square root of 21909453 is about 4680.7534649883. The cubic root of 21909453 is about 279.8189858946.

The spelling of 21909453 in words is "twenty-one million, nine hundred nine thousand, four hundred fifty-three".