21377947 has 2 divisors, whose sum is σ = 21377948. Its totient is φ = 21377946.

The previous prime is 21377929. The next prime is 21377957. The reversal of 21377947 is 74977312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21377947 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21377957) 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, 10688973 + 10688974.

It is an arithmetic number, because the mean of its divisors is an integer number (10688974).

Almost surely, 2^21377947 is an apocalyptic number.

21377947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21377947 is an equidigital number, since it uses as much as digits as its factorization.

21377947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 74088, while the sum is 40.

The square root of 21377947 is about 4623.6292022609. The cubic root of 21377947 is about 277.5377088058.

The spelling of 21377947 in words is "twenty-one million, three hundred seventy-seven thousand, nine hundred forty-seven".