21887491 has 2 divisors, whose sum is σ = 21887492. Its totient is φ = 21887490.

The previous prime is 21887479. The next prime is 21887507. The reversal of 21887491 is 19478812.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21887491 - 2⁹ = 21886979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21887401) 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, 10943745 + 10943746.

It is an arithmetic number, because the mean of its divisors is an integer number (10943746).

Almost surely, 2^21887491 is an apocalyptic number.

21887491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21887491 is an equidigital number, since it uses as much as digits as its factorization.

21887491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32256, while the sum is 40.

The square root of 21887491 is about 4678.4068869648. The cubic root of 21887491 is about 279.7254579383.

The spelling of 21887491 in words is "twenty-one million, eight hundred eighty-seven thousand, four hundred ninety-one".