21085577 has 2 divisors, whose sum is σ = 21085578. Its totient is φ = 21085576.

The previous prime is 21085567. The next prime is 21085583. The reversal of 21085577 is 77558012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20967241 + 118336 = 4579^2 + 344^2 .

It is a cyclic number.

It is not a de Polignac number, because 21085577 - 2¹⁸ = 20823433 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21085567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10542788 + 10542789.

It is an arithmetic number, because the mean of its divisors is an integer number (10542789).

Almost surely, 2^21085577 is an apocalyptic number.

It is an amenable number.

21085577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085577 is an equidigital number, since it uses as much as digits as its factorization.

21085577 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19600, while the sum is 35.

The square root of 21085577 is about 4591.9034179739. The cubic root of 21085577 is about 276.2666723488.

The spelling of 21085577 in words is "twenty-one million, eighty-five thousand, five hundred seventy-seven".