21809477 has 2 divisors, whose sum is σ = 21809478. Its totient is φ = 21809476.

The previous prime is 21809443. The next prime is 21809503. The reversal of 21809477 is 77490812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20484676 + 1324801 = 4526^2 + 1151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21809477 - 2⁶ = 21809413 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21809477.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21809377) 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, 10904738 + 10904739.

It is an arithmetic number, because the mean of its divisors is an integer number (10904739).

Almost surely, 2^21809477 is an apocalyptic number.

It is an amenable number.

21809477 is a deficient number, since it is larger than the sum of its proper divisors (1).

21809477 is an equidigital number, since it uses as much as digits as its factorization.

21809477 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 28224, while the sum is 38.

The square root of 21809477 is about 4670.0617768933. The cubic root of 21809477 is about 279.3927187070.

The spelling of 21809477 in words is "twenty-one million, eight hundred nine thousand, four hundred seventy-seven".