2105616781 has 2 divisors, whose sum is σ = 2105616782. Its totient is φ = 2105616780.

The previous prime is 2105616767. The next prime is 2105616797. The reversal of 2105616781 is 1876165012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1995051556 + 110565225 = 44666^2 + 10515^2 .

It is a cyclic number.

It is not a de Polignac number, because 2105616781 - 2⁵ = 2105616749 is a prime.

It is a super-2 number, since 2×2105616781² = 8867244056857603922, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 2105616781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2105616281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1052808390 + 1052808391.

It is an arithmetic number, because the mean of its divisors is an integer number (1052808391).

Almost surely, 2^2105616781 is an apocalyptic number.

It is an amenable number.

2105616781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2105616781 is an equidigital number, since it uses as much as digits as its factorization.

2105616781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20160, while the sum is 37.

The square root of 2105616781 is about 45887.0001307560. Note that the first 3 decimals coincide. The cubic root of 2105616781 is about 1281.7198522154.

The spelling of 2105616781 in words is "two billion, one hundred five million, six hundred sixteen thousand, seven hundred eighty-one".