20011199981 has 2 divisors, whose sum is σ = 20011199982. Its totient is φ = 20011199980.

The previous prime is 20011199963. The next prime is 20011200031. The reversal of 20011199981 is 18999111002.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13574347081 + 6436852900 = 116509^2 + 80230^2 .

It is a cyclic number.

It is not a de Polignac number, because 20011199981 - 2²² = 20007005677 is a prime.

It is a super-4 number, since 4×20011199981⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20011199921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10005599990 + 10005599991.

It is an arithmetic number, because the mean of its divisors is an integer number (10005599991).

Almost surely, 2^20011199981 is an apocalyptic number.

It is an amenable number.

20011199981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20011199981 is an equidigital number, since it uses as much as digits as its factorization.

20011199981 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 41.

The spelling of 20011199981 in words is "twenty billion, eleven million, one hundred ninety-nine thousand, nine hundred eighty-one".