20906145781 has 2 divisors, whose sum is σ = 20906145782. Its totient is φ = 20906145780.

The previous prime is 20906145773. The next prime is 20906145823. The reversal of 20906145781 is 18754160902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11672857681 + 9233288100 = 108041^2 + 96090^2 .

It is a cyclic number.

It is not a de Polignac number, because 20906145781 - 2³ = 20906145773 is a prime.

It is a super-2 number, since 2×20906145781² (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 (20906145731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10453072890 + 10453072891.

It is an arithmetic number, because the mean of its divisors is an integer number (10453072891).

Almost surely, 2^20906145781 is an apocalyptic number.

It is an amenable number.

20906145781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20906145781 is an equidigital number, since it uses as much as digits as its factorization.

20906145781 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 43.

The spelling of 20906145781 in words is "twenty billion, nine hundred six million, one hundred forty-five thousand, seven hundred eighty-one".