21663577 has 4 divisors (see below), whose sum is σ = 23330020. Its totient is φ = 19997136.

The previous prime is 21663547. The next prime is 21663589. The reversal of 21663577 is 77536612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11703241 + 9960336 = 3421^2 + 3156^2 .

It is a cyclic number.

It is not a de Polignac number, because 21663577 - 2²³ = 13274969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21663527) 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 in 3 ways as a sum of consecutive naturals, for example, 833202 + ... + 833227.

It is an arithmetic number, because the mean of its divisors is an integer number (5832505).

Almost surely, 2^21663577 is an apocalyptic number.

It is an amenable number.

21663577 is a deficient number, since it is larger than the sum of its proper divisors (1666443).

21663577 is a wasteful number, since it uses less digits than its factorization.

21663577 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1666442.

The product of its digits is 52920, while the sum is 37.

The square root of 21663577 is about 4654.4147859855. The cubic root of 21663577 is about 278.7683015325.

The spelling of 21663577 in words is "twenty-one million, six hundred sixty-three thousand, five hundred seventy-seven".