21166757 has 4 divisors (see below), whose sum is σ = 21176460. Its totient is φ = 21157056.

The previous prime is 21166721. The next prime is 21166763. The reversal of 21166757 is 75766112.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 8213956 + 12952801 = 2866^2 + 3599^2 .

It is a cyclic number.

It is not a de Polignac number, because 21166757 - 2¹⁰ = 21165733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21166787) 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, 119 + ... + 6507.

It is an arithmetic number, because the mean of its divisors is an integer number (5294115).

Almost surely, 2^21166757 is an apocalyptic number.

It is an amenable number.

21166757 is a deficient number, since it is larger than the sum of its proper divisors (9703).

21166757 is an equidigital number, since it uses as much as digits as its factorization.

21166757 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9702.

The product of its digits is 17640, while the sum is 35.

The square root of 21166757 is about 4600.7343978978. The cubic root of 21166757 is about 276.6207628556.

The spelling of 21166757 in words is "twenty-one million, one hundred sixty-six thousand, seven hundred fifty-seven".