21891907 has 2 divisors, whose sum is σ = 21891908. Its totient is φ = 21891906.

The previous prime is 21891889. The next prime is 21891911. The reversal of 21891907 is 70919812.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21891907 is a prime.

It is not a weakly prime, because it can be changed into another prime (21891967) 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, 10945953 + 10945954.

It is an arithmetic number, because the mean of its divisors is an integer number (10945954).

Almost surely, 2^21891907 is an apocalyptic number.

21891907 is a deficient number, since it is larger than the sum of its proper divisors (1).

21891907 is an equidigital number, since it uses as much as digits as its factorization.

21891907 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21891907 is about 4678.8788186915. The cubic root of 21891907 is about 279.7442690567.

It can be divided in two parts, 2189 and 1907, that added together give a 12-th power (4096 = 2¹²).

The spelling of 21891907 in words is "twenty-one million, eight hundred ninety-one thousand, nine hundred seven".