21580477 has 2 divisors, whose sum is σ = 21580478. Its totient is φ = 21580476.

The previous prime is 21580451. The next prime is 21580501. The reversal of 21580477 is 77408512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21031396 + 549081 = 4586^2 + 741^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21580477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21580577) 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, 10790238 + 10790239.

It is an arithmetic number, because the mean of its divisors is an integer number (10790239).

Almost surely, 2^21580477 is an apocalyptic number.

It is an amenable number.

21580477 is a deficient number, since it is larger than the sum of its proper divisors (1).

21580477 is an equidigital number, since it uses as much as digits as its factorization.

21580477 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 21580477 is about 4645.4792002548. The cubic root of 21580477 is about 278.4113994113.

Adding to 21580477 its reverse (77408512), we get a palindrome (98988989).

The spelling of 21580477 in words is "twenty-one million, five hundred eighty thousand, four hundred seventy-seven".