21661699793533 has 2 divisors, whose sum is σ = 21661699793534. Its totient is φ = 21661699793532.

The previous prime is 21661699793449. The next prime is 21661699793551. The reversal of 21661699793533 is 33539799616612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14667383359204 + 6994316434329 = 3829802^2 + 2644677^2 .

It is a cyclic number.

It is not a de Polignac number, because 21661699793533 - 2²¹ = 21661697696381 is a prime.

It is a super-2 number, since 2×21661699793533² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21661699794533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830849896766 + 10830849896767.

It is an arithmetic number, because the mean of its divisors is an integer number (10830849896767).

Almost surely, 2^{21661699793533} is an apocalyptic number.

It is an amenable number.

21661699793533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661699793533 is an equidigital number, since it uses as much as digits as its factorization.

21661699793533 is an evil number, because the sum of its binary digits is even.

The product of its digits is 297606960, while the sum is 70.

The spelling of 21661699793533 in words is "twenty-one trillion, six hundred sixty-one billion, six hundred ninety-nine million, seven hundred ninety-three thousand, five hundred thirty-three".