21009577 has 2 divisors, whose sum is σ = 21009578. Its totient is φ = 21009576.

The previous prime is 21009553. The next prime is 21009581. The reversal of 21009577 is 77590012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20575296 + 434281 = 4536^2 + 659^2 .

It is a cyclic number.

It is not a de Polignac number, because 21009577 - 2⁷ = 21009449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21009587) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504788 + 10504789.

It is an arithmetic number, because the mean of its divisors is an integer number (10504789).

Almost surely, 2^21009577 is an apocalyptic number.

It is an amenable number.

21009577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009577 is an equidigital number, since it uses as much as digits as its factorization.

21009577 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4410, while the sum is 31.

The square root of 21009577 is about 4583.6205122152. The cubic root of 21009577 is about 275.9343512909.

Adding to 21009577 its reverse (77590012), we get a palindrome (98599589).

The spelling of 21009577 in words is "twenty-one million, nine thousand, five hundred seventy-seven".