161721867851 has 2 divisors, whose sum is σ = 161721867852. Its totient is φ = 161721867850.

The previous prime is 161721867823. The next prime is 161721867863. The reversal of 161721867851 is 158768127161.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-161721867851 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 161721867793 and 161721867802.

It is not a weakly prime, because it can be changed into another prime (161721867551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80860933925 + 80860933926.

It is an arithmetic number, because the mean of its divisors is an integer number (80860933926).

Almost surely, 2^161721867851 is an apocalyptic number.

161721867851 is a deficient number, since it is larger than the sum of its proper divisors (1).

161721867851 is an equidigital number, since it uses as much as digits as its factorization.

161721867851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1128960, while the sum is 53.

The spelling of 161721867851 in words is "one hundred sixty-one billion, seven hundred twenty-one million, eight hundred sixty-seven thousand, eight hundred fifty-one".