21990541 has 2 divisors, whose sum is σ = 21990542. Its totient is φ = 21990540.

The previous prime is 21990523. The next prime is 21990557. The reversal of 21990541 is 14509912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13169641 + 8820900 = 3629^2 + 2970^2 .

It is a cyclic number.

It is not a de Polignac number, because 21990541 - 2⁵ = 21990509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21990041) 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, 10995270 + 10995271.

It is an arithmetic number, because the mean of its divisors is an integer number (10995271).

Almost surely, 2^21990541 is an apocalyptic number.

It is an amenable number.

21990541 is a deficient number, since it is larger than the sum of its proper divisors (1).

21990541 is an equidigital number, since it uses as much as digits as its factorization.

21990541 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 21990541 is about 4689.4073186278. The cubic root of 21990541 is about 280.1637689905.

The spelling of 21990541 in words is "twenty-one million, nine hundred ninety thousand, five hundred forty-one".