21696977 has 2 divisors, whose sum is σ = 21696978. Its totient is φ = 21696976.

The previous prime is 21696973. The next prime is 21696979. The reversal of 21696977 is 77969612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17048641 + 4648336 = 4129^2 + 2156^2 .

It is a cyclic number.

It is not a de Polignac number, because 21696977 - 2² = 21696973 is a prime.

Together with 21696979, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21696973) 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, 10848488 + 10848489.

It is an arithmetic number, because the mean of its divisors is an integer number (10848489).

Almost surely, 2^21696977 is an apocalyptic number.

It is an amenable number.

21696977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21696977 is an equidigital number, since it uses as much as digits as its factorization.

21696977 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 285768, while the sum is 47.

The square root of 21696977 is about 4658.0013954485. The cubic root of 21696977 is about 278.9114924182.

The spelling of 21696977 in words is "twenty-one million, six hundred ninety-six thousand, nine hundred seventy-seven".