21953267561 has 2 divisors, whose sum is σ = 21953267562. Its totient is φ = 21953267560.

The previous prime is 21953267537. The next prime is 21953267597. The reversal of 21953267561 is 16576235912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11953267561 + 10000000000 = 109331^2 + 100000^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21953267561 is a prime.

It is not a weakly prime, because it can be changed into another prime (21953264561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10976633780 + 10976633781.

It is an arithmetic number, because the mean of its divisors is an integer number (10976633781).

Almost surely, 2^21953267561 is an apocalyptic number.

It is an amenable number.

21953267561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21953267561 is an equidigital number, since it uses as much as digits as its factorization.

21953267561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 680400, while the sum is 47.

The spelling of 21953267561 in words is "twenty-one billion, nine hundred fifty-three million, two hundred sixty-seven thousand, five hundred sixty-one".