21099609977 has 2 divisors, whose sum is σ = 21099609978. Its totient is φ = 21099609976.

The previous prime is 21099609967. The next prime is 21099609983. The reversal of 21099609977 is 77990699012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20731392256 + 368217721 = 143984^2 + 19189^2 .

It is a cyclic number.

It is not a de Polignac number, because 21099609977 - 2⁴ = 21099609961 is a prime.

It is not a weakly prime, because it can be changed into another prime (21099609967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10549804988 + 10549804989.

It is an arithmetic number, because the mean of its divisors is an integer number (10549804989).

Almost surely, 2^21099609977 is an apocalyptic number.

It is an amenable number.

21099609977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21099609977 is an equidigital number, since it uses as much as digits as its factorization.

21099609977 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3857868, while the sum is 59.

The spelling of 21099609977 in words is "twenty-one billion, ninety-nine million, six hundred nine thousand, nine hundred seventy-seven".