20678921 has 2 divisors, whose sum is σ = 20678922. Its totient is φ = 20678920.

The previous prime is 20678899. The next prime is 20678923. The reversal of 20678921 is 12987602.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10368400 + 10310521 = 3220^2 + 3211^2 .

It is a cyclic number.

It is not a de Polignac number, because 20678921 - 2⁶ = 20678857 is a prime.

Together with 20678923, 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 (20678923) 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, 10339460 + 10339461.

It is an arithmetic number, because the mean of its divisors is an integer number (10339461).

Almost surely, 2^20678921 is an apocalyptic number.

It is an amenable number.

20678921 is a deficient number, since it is larger than the sum of its proper divisors (1).

20678921 is an equidigital number, since it uses as much as digits as its factorization.

20678921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 20678921 is about 4547.4081628989. The cubic root of 20678921 is about 274.4791065304.

The spelling of 20678921 in words is "twenty million, six hundred seventy-eight thousand, nine hundred twenty-one".