20978549 has 2 divisors, whose sum is σ = 20978550. Its totient is φ = 20978548.

The previous prime is 20978533. The next prime is 20978557. The reversal of 20978549 is 94587902.

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., 18232900 + 2745649 = 4270^2 + 1657^2 .

It is a cyclic number.

It is not a de Polignac number, because 20978549 - 2⁴ = 20978533 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20978569) 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, 10489274 + 10489275.

It is an arithmetic number, because the mean of its divisors is an integer number (10489275).

Almost surely, 2^20978549 is an apocalyptic number.

It is an amenable number.

20978549 is a deficient number, since it is larger than the sum of its proper divisors (1).

20978549 is an equidigital number, since it uses as much as digits as its factorization.

20978549 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 181440, while the sum is 44.

The square root of 20978549 is about 4580.2346009784. The cubic root of 20978549 is about 275.7984464558.

The spelling of 20978549 in words is "twenty million, nine hundred seventy-eight thousand, five hundred forty-nine".