21661031332091 has 2 divisors, whose sum is σ = 21661031332092. Its totient is φ = 21661031332090.

The previous prime is 21661031332081. The next prime is 21661031332123. The reversal of 21661031332091 is 19023313016612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21661031332091 is a prime.

It is not a weakly prime, because it can be changed into another prime (21661031332081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830515666045 + 10830515666046.

It is an arithmetic number, because the mean of its divisors is an integer number (10830515666046).

Almost surely, 2^{21661031332091} is an apocalyptic number.

21661031332091 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661031332091 is an equidigital number, since it uses as much as digits as its factorization.

21661031332091 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 34992, while the sum is 38.

The spelling of 21661031332091 in words is "twenty-one trillion, six hundred sixty-one billion, thirty-one million, three hundred thirty-two thousand, ninety-one".