20978779 has 8 divisors (see below), whose sum is σ = 21542400. Its totient is φ = 20420136.

The previous prime is 20978773. The next prime is 20978791. The reversal of 20978779 is 97787902.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20978779 - 2⁹ = 20978267 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20978773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8232 + ... + 10474.

It is an arithmetic number, because the mean of its divisors is an integer number (2692800).

Almost surely, 2^20978779 is an apocalyptic number.

20978779 is a deficient number, since it is larger than the sum of its proper divisors (563621).

20978779 is a wasteful number, since it uses less digits than its factorization.

20978779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2489.

The product of its (nonzero) digits is 444528, while the sum is 49.

The square root of 20978779 is about 4580.2597087938. The cubic root of 20978779 is about 275.7994543649.

The spelling of 20978779 in words is "twenty million, nine hundred seventy-eight thousand, seven hundred seventy-nine".