16861457521 has 2 divisors, whose sum is σ = 16861457522. Its totient is φ = 16861457520.

The previous prime is 16861457519. The next prime is 16861457533. The reversal of 16861457521 is 12575416861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15666026896 + 1195430625 = 125164^2 + 34575^2 .

It is a cyclic number.

It is not a de Polignac number, because 16861457521 - 2¹ = 16861457519 is a prime.

Together with 16861457519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (16861458521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8430728760 + 8430728761.

It is an arithmetic number, because the mean of its divisors is an integer number (8430728761).

Almost surely, 2^16861457521 is an apocalyptic number.

It is an amenable number.

16861457521 is a deficient number, since it is larger than the sum of its proper divisors (1).

16861457521 is an equidigital number, since it uses as much as digits as its factorization.

16861457521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 403200, while the sum is 46.

The spelling of 16861457521 in words is "sixteen billion, eight hundred sixty-one million, four hundred fifty-seven thousand, five hundred twenty-one".