21156779 has 12 divisors (see below), whose sum is σ = 25213608. Its totient is φ = 17690400.

The previous prime is 21156769. The next prime is 21156809. The reversal of 21156779 is 97765112.

It is not a de Polignac number, because 21156779 - 2⁴ = 21156763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21156719) 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 11 ways as a sum of consecutive naturals, for example, 3257 + ... + 7274.

It is an arithmetic number, because the mean of its divisors is an integer number (2101134).

Almost surely, 2^21156779 is an apocalyptic number.

21156779 is a deficient number, since it is larger than the sum of its proper divisors (4056829).

21156779 is a wasteful number, since it uses less digits than its factorization.

21156779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10586 (or 10579 counting only the distinct ones).

The product of its digits is 26460, while the sum is 38.

The square root of 21156779 is about 4599.6498779798. The cubic root of 21156779 is about 276.5772897216.

The spelling of 21156779 in words is "twenty-one million, one hundred fifty-six thousand, seven hundred seventy-nine".