21105977 has 2 divisors, whose sum is σ = 21105978. Its totient is φ = 21105976.

The previous prime is 21105971. The next prime is 21106037. The reversal of 21105977 is 77950112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17480761 + 3625216 = 4181^2 + 1904^2 .

It is a cyclic number.

It is not a de Polignac number, because 21105977 - 2⁶ = 21105913 is a prime.

It is not a weakly prime, because it can be changed into another prime (21105971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552988 + 10552989.

It is an arithmetic number, because the mean of its divisors is an integer number (10552989).

Almost surely, 2^21105977 is an apocalyptic number.

It is an amenable number.

21105977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21105977 is an equidigital number, since it uses as much as digits as its factorization.

21105977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4410, while the sum is 32.

The square root of 21105977 is about 4594.1241820395. The cubic root of 21105977 is about 276.3557383418.

The spelling of 21105977 in words is "twenty-one million, one hundred five thousand, nine hundred seventy-seven".