21721067 has 2 divisors, whose sum is σ = 21721068. Its totient is φ = 21721066.

The previous prime is 21721057. The next prime is 21721081. The reversal of 21721067 is 76012712.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21721067 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21721057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10860533 + 10860534.

It is an arithmetic number, because the mean of its divisors is an integer number (10860534).

Almost surely, 2^21721067 is an apocalyptic number.

21721067 is a deficient number, since it is larger than the sum of its proper divisors (1).

21721067 is an equidigital number, since it uses as much as digits as its factorization.

21721067 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1176, while the sum is 26.

The square root of 21721067 is about 4660.5865510684. The cubic root of 21721067 is about 279.0146787239.

Adding to 21721067 its reverse (76012712), we get a palindrome (97733779).

The spelling of 21721067 in words is "twenty-one million, seven hundred twenty-one thousand, sixty-seven".