20986921 has 2 divisors, whose sum is σ = 20986922. Its totient is φ = 20986920.

The previous prime is 20986919. The next prime is 20986943. The reversal of 20986921 is 12968902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20602521 + 384400 = 4539^2 + 620^2 .

It is a cyclic number.

It is not a de Polignac number, because 20986921 - 2¹ = 20986919 is a prime.

Together with 20986919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20986991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10493460 + 10493461.

It is an arithmetic number, because the mean of its divisors is an integer number (10493461).

Almost surely, 2^20986921 is an apocalyptic number.

It is an amenable number.

20986921 is a deficient number, since it is larger than the sum of its proper divisors (1).

20986921 is an equidigital number, since it uses as much as digits as its factorization.

20986921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 20986921 is about 4581.1484368005. The cubic root of 20986921 is about 275.8351296015.

The spelling of 20986921 in words is "twenty million, nine hundred eighty-six thousand, nine hundred twenty-one".