20905571261 has 2 divisors, whose sum is σ = 20905571262. Its totient is φ = 20905571260.

The previous prime is 20905571231. The next prime is 20905571287. The reversal of 20905571261 is 16217550902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20784988900 + 120582361 = 144170^2 + 10981^2 .

It is a cyclic number.

It is not a de Polignac number, because 20905571261 - 2¹⁴ = 20905554877 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20905571201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10452785630 + 10452785631.

It is an arithmetic number, because the mean of its divisors is an integer number (10452785631).

Almost surely, 2^20905571261 is an apocalyptic number.

It is an amenable number.

20905571261 is a deficient number, since it is larger than the sum of its proper divisors (1).

20905571261 is an equidigital number, since it uses as much as digits as its factorization.

20905571261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37800, while the sum is 38.

The spelling of 20905571261 in words is "twenty billion, nine hundred five million, five hundred seventy-one thousand, two hundred sixty-one".