20851643 has 2 divisors, whose sum is σ = 20851644. Its totient is φ = 20851642.

The previous prime is 20851637. The next prime is 20851679. The reversal of 20851643 is 34615802.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20851643 - 2²⁰ = 19803067 is a prime.

It is not a weakly prime, because it can be changed into another prime (20851693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10425821 + 10425822.

It is an arithmetic number, because the mean of its divisors is an integer number (10425822).

Almost surely, 2^20851643 is an apocalyptic number.

20851643 is a deficient number, since it is larger than the sum of its proper divisors (1).

20851643 is an equidigital number, since it uses as much as digits as its factorization.

20851643 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 20851643 is about 4566.3599288711. The cubic root of 20851643 is about 275.2411900542.

The spelling of 20851643 in words is "twenty million, eight hundred fifty-one thousand, six hundred forty-three".