20878981 has 2 divisors, whose sum is σ = 20878982. Its totient is φ = 20878980.

The previous prime is 20878969. The next prime is 20878987. The reversal of 20878981 is 18987802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20848356 + 30625 = 4566^2 + 175^2 .

It is a cyclic number.

It is not a de Polignac number, because 20878981 - 2¹⁵ = 20846213 is a prime.

It is a super-2 number, since 2×20878981² = 871863695196722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20878987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10439490 + 10439491.

It is an arithmetic number, because the mean of its divisors is an integer number (10439491).

Almost surely, 2^20878981 is an apocalyptic number.

It is an amenable number.

20878981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20878981 is an equidigital number, since it uses as much as digits as its factorization.

20878981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64512, while the sum is 43.

The square root of 20878981 is about 4569.3523611120. The cubic root of 20878981 is about 275.3614245067.

The spelling of 20878981 in words is "twenty million, eight hundred seventy-eight thousand, nine hundred eighty-one".