21121766 has 4 divisors (see below), whose sum is σ = 31682652. Its totient is φ = 10560882.

The previous prime is 21121759. The next prime is 21121781. The reversal of 21121766 is 66712112.

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

It is a super-2 number, since 2×21121766² = 892257997917512, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5280440 + ... + 5280443.

It is an arithmetic number, because the mean of its divisors is an integer number (7920663).

Almost surely, 2^21121766 is an apocalyptic number.

21121766 is a deficient number, since it is larger than the sum of its proper divisors (10560886).

21121766 is a wasteful number, since it uses less digits than its factorization.

21121766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10560885.

The product of its digits is 1008, while the sum is 26.

The square root of 21121766 is about 4595.8422514268. The cubic root of 21121766 is about 276.4246334096.

Adding to 21121766 its reverse (66712112), we get a palindrome (87833878).

The spelling of 21121766 in words is "twenty-one million, one hundred twenty-one thousand, seven hundred sixty-six".