21000779 has 2 divisors, whose sum is σ = 21000780. Its totient is φ = 21000778.

The previous prime is 21000761. The next prime is 21000803. The reversal of 21000779 is 97700012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21000779 - 2²⁴ = 4223563 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21000709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500389 + 10500390.

It is an arithmetic number, because the mean of its divisors is an integer number (10500390).

Almost surely, 2^21000779 is an apocalyptic number.

21000779 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000779 is an equidigital number, since it uses as much as digits as its factorization.

21000779 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 882, while the sum is 26.

The square root of 21000779 is about 4582.6606900359. The cubic root of 21000779 is about 275.8958290276.

The spelling of 21000779 in words is "twenty-one million, seven hundred seventy-nine", and thus it is an aban number.