20621172681 has 12 divisors (see below), whose sum is σ = 29916211780. Its totient is φ = 13687414560.

The previous prime is 20621172619. The next prime is 20621172731. The reversal of 20621172681 is 18627112602.

20621172681 is a `hidden beast` number, since 2 + 0 + 621 + 1 + 7 + 26 + 8 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 19297377225 + 1323795456 = 138915^2 + 36384^2 .

It is not a de Polignac number, because 20621172681 - 2⁷ = 20621172553 is a prime.

It is a super-2 number, since 2×20621172681² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20621172281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5000650 + ... + 5004771.

Almost surely, 2^20621172681 is an apocalyptic number.

It is an amenable number.

20621172681 is a deficient number, since it is larger than the sum of its proper divisors (9295039099).

20621172681 is a wasteful number, since it uses less digits than its factorization.

20621172681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10005656 (or 10005653 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 36.

The spelling of 20621172681 in words is "twenty billion, six hundred twenty-one million, one hundred seventy-two thousand, six hundred eighty-one".