21778077 has 4 divisors (see below), whose sum is σ = 29037440. Its totient is φ = 14518716.

The previous prime is 21778069. The next prime is 21778109. The reversal of 21778077 is 77087712.

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 not a de Polignac number, because 21778077 - 2³ = 21778069 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 (21778007) 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, 3629677 + ... + 3629682.

It is an arithmetic number, because the mean of its divisors is an integer number (7259360).

Almost surely, 2^21778077 is an apocalyptic number.

It is an amenable number.

21778077 is a deficient number, since it is larger than the sum of its proper divisors (7259363).

21778077 is an equidigital number, since it uses as much as digits as its factorization.

21778077 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7259362.

The product of its (nonzero) digits is 38416, while the sum is 39.

The square root of 21778077 is about 4666.6987260804. The cubic root of 21778077 is about 279.2585699149.

The spelling of 21778077 in words is "twenty-one million, seven hundred seventy-eight thousand, seventy-seven".