21661165732387 has 2 divisors, whose sum is σ = 21661165732388. Its totient is φ = 21661165732386.

The previous prime is 21661165732379. The next prime is 21661165732429. The reversal of 21661165732387 is 78323756116612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21661165732387 - 2³ = 21661165732379 is a prime.

It is a super-2 number, since 2×21661165732387² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21661165736387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830582866193 + 10830582866194.

It is an arithmetic number, because the mean of its divisors is an integer number (10830582866194).

Almost surely, 2^{21661165732387} is an apocalyptic number.

21661165732387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661165732387 is an equidigital number, since it uses as much as digits as its factorization.

21661165732387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15240960, while the sum is 58.

The spelling of 21661165732387 in words is "twenty-one trillion, six hundred sixty-one billion, one hundred sixty-five million, seven hundred thirty-two thousand, three hundred eighty-seven".