21320947 has 2 divisors, whose sum is σ = 21320948. Its totient is φ = 21320946.

The previous prime is 21320921. The next prime is 21320969. The reversal of 21320947 is 74902312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21320947 is a prime.

It is not a weakly prime, because it can be changed into another prime (21320987) by changing a digit.

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 as a sum of consecutive naturals, namely, 10660473 + 10660474.

It is an arithmetic number, because the mean of its divisors is an integer number (10660474).

Almost surely, 2^21320947 is an apocalyptic number.

21320947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320947 is an equidigital number, since it uses as much as digits as its factorization.

21320947 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 28.

The square root of 21320947 is about 4617.4610989157. The cubic root of 21320947 is about 277.2908230744.

The spelling of 21320947 in words is "twenty-one million, three hundred twenty thousand, nine hundred forty-seven".