21005294 has 4 divisors (see below), whose sum is σ = 31507944. Its totient is φ = 10502646.

The previous prime is 21005293. The next prime is 21005297. The reversal of 21005294 is 49250012.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21005291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5251322 + ... + 5251325.

It is an arithmetic number, because the mean of its divisors is an integer number (7876986).

Almost surely, 2^21005294 is an apocalyptic number.

21005294 is a deficient number, since it is larger than the sum of its proper divisors (10502650).

21005294 is a wasteful number, since it uses less digits than its factorization.

21005294 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10502649.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21005294 is about 4583.1532813119. The cubic root of 21005294 is about 275.9155994118.

The spelling of 21005294 in words is "twenty-one million, five thousand, two hundred ninety-four".