21779021 has 4 divisors (see below), whose sum is σ = 23758944. Its totient is φ = 19799100.

The previous prime is 21779011. The next prime is 21779033. The reversal of 21779021 is 12097712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21779021 - 2¹⁰ = 21777997 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21779011) by changing a digit.

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 in 3 ways as a sum of consecutive naturals, for example, 989945 + ... + 989966.

It is an arithmetic number, because the mean of its divisors is an integer number (5939736).

Almost surely, 2^21779021 is an apocalyptic number.

It is an amenable number.

21779021 is a deficient number, since it is larger than the sum of its proper divisors (1979923).

21779021 is a wasteful number, since it uses less digits than its factorization.

21779021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1979922.

The product of its (nonzero) digits is 1764, while the sum is 29.

The square root of 21779021 is about 4666.7998671467. The cubic root of 21779021 is about 279.2626048025.

The spelling of 21779021 in words is "twenty-one million, seven hundred seventy-nine thousand, twenty-one".