21571867 has 2 divisors, whose sum is σ = 21571868. Its totient is φ = 21571866.

The previous prime is 21571841. The next prime is 21571903. The reversal of 21571867 is 76817512.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21571867 is a prime.

It is not a weakly prime, because it can be changed into another prime (21571817) 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, 10785933 + 10785934.

It is an arithmetic number, because the mean of its divisors is an integer number (10785934).

Almost surely, 2^21571867 is an apocalyptic number.

21571867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21571867 is an equidigital number, since it uses as much as digits as its factorization.

21571867 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 23520, while the sum is 37.

The square root of 21571867 is about 4644.5524003934. The cubic root of 21571867 is about 278.3743683946.

The spelling of 21571867 in words is "twenty-one million, five hundred seventy-one thousand, eight hundred sixty-seven".