20421665651443 has 4 divisors (see below), whose sum is σ = 23339046458800. Its totient is φ = 17504284844088.

The previous prime is 20421665651311. The next prime is 20421665651459. The reversal of 20421665651443 is 34415656612402.

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

It is not a de Polignac number, because 20421665651443 - 2¹⁷ = 20421665520371 is a prime.

It is a super-3 number, since 3×20421665651443³ (a number of 41 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20421665651743) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1458690403668 + ... + 1458690403681.

It is an arithmetic number, because the mean of its divisors is an integer number (5834761614700).

Almost surely, 2^{20421665651443} is an apocalyptic number.

20421665651443 is a deficient number, since it is larger than the sum of its proper divisors (2917380807357).

20421665651443 is an equidigital number, since it uses as much as digits as its factorization.

20421665651443 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2917380807356.

The product of its (nonzero) digits is 4147200, while the sum is 49.

The spelling of 20421665651443 in words is "twenty trillion, four hundred twenty-one billion, six hundred sixty-five million, six hundred fifty-one thousand, four hundred forty-three".