21661465731901 has 2 divisors, whose sum is σ = 21661465731902. Its totient is φ = 21661465731900.

The previous prime is 21661465731881. The next prime is 21661465731943. The reversal of 21661465731901 is 10913756416612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21191761109401 + 469704622500 = 4603451^2 + 685350^2 .

It is a cyclic number.

It is not a de Polignac number, because 21661465731901 - 2⁵ = 21661465731869 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21661460731901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830732865950 + 10830732865951.

It is an arithmetic number, because the mean of its divisors is an integer number (10830732865951).

Almost surely, 2^{21661465731901} is an apocalyptic number.

It is an amenable number.

21661465731901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661465731901 is an equidigital number, since it uses as much as digits as its factorization.

21661465731901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1632960, while the sum is 52.

The spelling of 21661465731901 in words is "twenty-one trillion, six hundred sixty-one billion, four hundred sixty-five million, seven hundred thirty-one thousand, nine hundred one".