20616620581 has 2 divisors, whose sum is σ = 20616620582. Its totient is φ = 20616620580.

The previous prime is 20616620551. The next prime is 20616620597. The reversal of 20616620581 is 18502661602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18045623556 + 2570997025 = 134334^2 + 50705^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20616620581 is a prime.

It is a super-2 number, since 2×20616620581² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20616620581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20616620551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10308310290 + 10308310291.

It is an arithmetic number, because the mean of its divisors is an integer number (10308310291).

Almost surely, 2^20616620581 is an apocalyptic number.

It is an amenable number.

20616620581 is a deficient number, since it is larger than the sum of its proper divisors (1).

20616620581 is an equidigital number, since it uses as much as digits as its factorization.

20616620581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 34560, while the sum is 37.

The spelling of 20616620581 in words is "twenty billion, six hundred sixteen million, six hundred twenty thousand, five hundred eighty-one".