21046945 has 4 divisors (see below), whose sum is σ = 25256340. Its totient is φ = 16837552.

The previous prime is 21046939. The next prime is 21046951. The reversal of 21046945 is 54964012.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21046939) and next prime (21046951).

It can be written as a sum of positive squares in 2 ways, for example, as 16136289 + 4910656 = 4017^2 + 2216^2 .

It is a cyclic number.

It is not a de Polignac number, because 21046945 - 2²¹ = 18949793 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2104690 + ... + 2104699.

It is an arithmetic number, because the mean of its divisors is an integer number (6314085).

Almost surely, 2^21046945 is an apocalyptic number.

It is an amenable number.

21046945 is a deficient number, since it is larger than the sum of its proper divisors (4209395).

21046945 is an equidigital number, since it uses as much as digits as its factorization.

21046945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4209394.

The product of its (nonzero) digits is 8640, while the sum is 31.

The square root of 21046945 is about 4587.6949549856. The cubic root of 21046945 is about 276.0978482792.

The spelling of 21046945 in words is "twenty-one million, forty-six thousand, nine hundred forty-five".