20641643 has 4 divisors (see below), whose sum is σ = 22518168. Its totient is φ = 18765120.

The previous prime is 20641633. The next prime is 20641661. The reversal of 20641643 is 34614602.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 20641643 - 2⁴ = 20641627 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20641633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 938246 + ... + 938267.

It is an arithmetic number, because the mean of its divisors is an integer number (5629542).

Almost surely, 2^20641643 is an apocalyptic number.

20641643 is the 2429-th centered heptagonal number.

20641643 is a deficient number, since it is larger than the sum of its proper divisors (1876525).

20641643 is a wasteful number, since it uses less digits than its factorization.

20641643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1876524.

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 20641643 is about 4543.3074956468. The cubic root of 20641643 is about 274.3140723434.

The spelling of 20641643 in words is "twenty million, six hundred forty-one thousand, six hundred forty-three".