21118779 has 32 divisors (see below), whose sum is σ = 34394880. Its totient is φ = 12700800.

The previous prime is 21118771. The next prime is 21118787. The reversal of 21118779 is 97781112.

It is an interprime number because it is at equal distance from previous prime (21118771) and next prime (21118787).

It is not a de Polignac number, because 21118779 - 2³ = 21118771 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118771) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 62499 + ... + 62835.

It is an arithmetic number, because the mean of its divisors is an integer number (1074840).

Almost surely, 2^21118779 is an apocalyptic number.

21118779 is a deficient number, since it is larger than the sum of its proper divisors (13276101).

21118779 is a wasteful number, since it uses less digits than its factorization.

21118779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 568 (or 562 counting only the distinct ones).

The product of its digits is 7056, while the sum is 36.

The square root of 21118779 is about 4595.5172722992. The cubic root of 21118779 is about 276.4116023132.

The spelling of 21118779 in words is "twenty-one million, one hundred eighteen thousand, seven hundred seventy-nine".