20697779 has 2 divisors, whose sum is σ = 20697780. Its totient is φ = 20697778.

The previous prime is 20697757. The next prime is 20697797. The reversal of 20697779 is 97779602.

Together with next prime (20697797) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20697779 - 2¹⁶ = 20632243 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (20697709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10348889 + 10348890.

It is an arithmetic number, because the mean of its divisors is an integer number (10348890).

Almost surely, 2^20697779 is an apocalyptic number.

20697779 is a deficient number, since it is larger than the sum of its proper divisors (1).

20697779 is an equidigital number, since it uses as much as digits as its factorization.

20697779 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 333396, while the sum is 47.

The square root of 20697779 is about 4549.4811792115. The cubic root of 20697779 is about 274.5625176256.

The spelling of 20697779 in words is "twenty million, six hundred ninety-seven thousand, seven hundred seventy-nine".