20999977 has 2 divisors, whose sum is σ = 20999978. Its totient is φ = 20999976.

The previous prime is 20999941. The next prime is 20999999. The reversal of 20999977 is 77999902.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12362256 + 8637721 = 3516^2 + 2939^2 .

It is a cyclic number.

It is not a de Polignac number, because 20999977 - 2¹⁵ = 20967209 is a prime.

It is not a weakly prime, because it can be changed into another prime (20999917) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10499988 + 10499989.

It is an arithmetic number, because the mean of its divisors is an integer number (10499989).

Almost surely, 2^20999977 is an apocalyptic number.

It is an amenable number.

20999977 is a deficient number, since it is larger than the sum of its proper divisors (1).

20999977 is an equidigital number, since it uses as much as digits as its factorization.

20999977 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 642978, while the sum is 52.

The square root of 20999977 is about 4582.5731854494. The cubic root of 20999977 is about 275.8923169154.

The spelling of 20999977 in words is "twenty million, nine hundred ninety-nine thousand, nine hundred seventy-seven".