21661353004691 has 2 divisors, whose sum is σ = 21661353004692. Its totient is φ = 21661353004690.

The previous prime is 21661353004679. The next prime is 21661353004693. The reversal of 21661353004691 is 19640035316612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21661353004691 is a prime.

Together with 21661353004693, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21661353004693) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830676502345 + 10830676502346.

It is an arithmetic number, because the mean of its divisors is an integer number (10830676502346).

Almost surely, 2^{21661353004691} is an apocalyptic number.

21661353004691 is a deficient number, since it is larger than the sum of its proper divisors (1).

21661353004691 is an equidigital number, since it uses as much as digits as its factorization.

21661353004691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 699840, while the sum is 47.

The spelling of 21661353004691 in words is "twenty-one trillion, six hundred sixty-one billion, three hundred fifty-three million, four thousand, six hundred ninety-one".