20643275621 has 2 divisors, whose sum is σ = 20643275622. Its totient is φ = 20643275620.

The previous prime is 20643275603. The next prime is 20643275677. The reversal of 20643275621 is 12657234602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14880340225 + 5762935396 = 121985^2 + 75914^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20643275621 is a prime.

It is a super-2 number, since 2×20643275621² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20643275221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10321637810 + 10321637811.

It is an arithmetic number, because the mean of its divisors is an integer number (10321637811).

Almost surely, 2^20643275621 is an apocalyptic number.

It is an amenable number.

20643275621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20643275621 is an equidigital number, since it uses as much as digits as its factorization.

20643275621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120960, while the sum is 38.

The spelling of 20643275621 in words is "twenty billion, six hundred forty-three million, two hundred seventy-five thousand, six hundred twenty-one".