21047291 has 4 divisors (see below), whose sum is σ = 21123552. Its totient is φ = 20971032.

The previous prime is 21047281. The next prime is 21047303. The reversal of 21047291 is 19274012.

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

It is a cyclic number.

It is not a de Polignac number, because 21047291 - 2¹⁸ = 20785147 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21047291.

It is not an unprimeable number, because it can be changed into a prime (21047281) 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, 37715 + ... + 38268.

It is an arithmetic number, because the mean of its divisors is an integer number (5280888).

Almost surely, 2^21047291 is an apocalyptic number.

21047291 is a deficient number, since it is larger than the sum of its proper divisors (76261).

21047291 is an equidigital number, since it uses as much as digits as its factorization.

21047291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 76260.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 21047291 is about 4587.7326643997. The cubic root of 21047291 is about 276.0993612356.

The spelling of 21047291 in words is "twenty-one million, forty-seven thousand, two hundred ninety-one".