21354805 has 8 divisors (see below), whose sum is σ = 27133272. Its totient is φ = 16078848.

The previous prime is 21354799. The next prime is 21354847. The reversal of 21354805 is 50845312.

It can be written as a sum of positive squares in 4 ways, for example, as 4363921 + 16990884 = 2089^2 + 4122^2 .

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 21354805 - 2³ = 21354797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 125532 + ... + 125701.

It is an arithmetic number, because the mean of its divisors is an integer number (3391659).

Almost surely, 2^21354805 is an apocalyptic number.

It is an amenable number.

21354805 is a deficient number, since it is larger than the sum of its proper divisors (5778467).

21354805 is a wasteful number, since it uses less digits than its factorization.

21354805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251255.

The product of its (nonzero) digits is 4800, while the sum is 28.

The square root of 21354805 is about 4621.1259450485. The cubic root of 21354805 is about 277.4375261792.

The spelling of 21354805 in words is "twenty-one million, three hundred fifty-four thousand, eight hundred five".