20847977 has 2 divisors, whose sum is σ = 20847978. Its totient is φ = 20847976.

The previous prime is 20847973. The next prime is 20847979. The reversal of 20847977 is 77974802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15178816 + 5669161 = 3896^2 + 2381^2 .

It is a cyclic number.

It is not a de Polignac number, because 20847977 - 2² = 20847973 is a prime.

Together with 20847979, 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 (20847971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10423988 + 10423989.

It is an arithmetic number, because the mean of its divisors is an integer number (10423989).

Almost surely, 2^20847977 is an apocalyptic number.

It is an amenable number.

20847977 is a deficient number, since it is larger than the sum of its proper divisors (1).

20847977 is an equidigital number, since it uses as much as digits as its factorization.

20847977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 197568, while the sum is 44.

The square root of 20847977 is about 4565.9584974023. The cubic root of 20847977 is about 275.2250587379.

The spelling of 20847977 in words is "twenty million, eight hundred forty-seven thousand, nine hundred seventy-seven".