21000977 has 2 divisors, whose sum is σ = 21000978. Its totient is φ = 21000976.

The previous prime is 21000953. The next prime is 21000983. The reversal of 21000977 is 77900012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18011536 + 2989441 = 4244^2 + 1729^2 .

It is a cyclic number.

It is not a de Polignac number, because 21000977 - 2⁶ = 21000913 is a prime.

It is not a weakly prime, because it can be changed into another prime (21000907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500488 + 10500489.

It is an arithmetic number, because the mean of its divisors is an integer number (10500489).

Almost surely, 2^21000977 is an apocalyptic number.

It is an amenable number.

21000977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000977 is an equidigital number, since it uses as much as digits as its factorization.

21000977 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21000977 is about 4582.6822931554. The cubic root of 21000977 is about 275.8966960939.

Adding to 21000977 its reverse (77900012), we get a palindrome (98900989).

The spelling of 21000977 in words is "twenty-one million, nine hundred seventy-seven", and thus it is an aban number.