20686943021 has 4 divisors (see below), whose sum is σ = 20887787232. Its totient is φ = 20486098812.

The previous prime is 20686942999. The next prime is 20686943029. The reversal of 20686943021 is 12034968602.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12034968602 = 2 ⋅6017484301.

It is a cyclic number.

It is not a de Polignac number, because 20686943021 - 2⁶ = 20686942957 is a prime.

It is a super-2 number, since 2×20686943021² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20686943021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20686943029) 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, 100421951 + ... + 100422156.

It is an arithmetic number, because the mean of its divisors is an integer number (5221946808).

Almost surely, 2^20686943021 is an apocalyptic number.

It is an amenable number.

20686943021 is a deficient number, since it is larger than the sum of its proper divisors (200844211).

20686943021 is a wasteful number, since it uses less digits than its factorization.

20686943021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 200844210.

The product of its (nonzero) digits is 124416, while the sum is 41.

The spelling of 20686943021 in words is "twenty billion, six hundred eighty-six million, nine hundred forty-three thousand, twenty-one".