16251109781 has 2 divisors, whose sum is σ = 16251109782. Its totient is φ = 16251109780.

The previous prime is 16251109753. The next prime is 16251109837. The reversal of 16251109781 is 18790115261.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14409841681 + 1841268100 = 120041^2 + 42910^2 .

It is a cyclic number.

It is not a de Polignac number, because 16251109781 - 2⁶ = 16251109717 is a prime.

It is a super-2 number, since 2×16251109781² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16251109711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8125554890 + 8125554891.

It is an arithmetic number, because the mean of its divisors is an integer number (8125554891).

Almost surely, 2^16251109781 is an apocalyptic number.

It is an amenable number.

16251109781 is a deficient number, since it is larger than the sum of its proper divisors (1).

16251109781 is an equidigital number, since it uses as much as digits as its factorization.

16251109781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30240, while the sum is 41.

The spelling of 16251109781 in words is "sixteen billion, two hundred fifty-one million, one hundred nine thousand, seven hundred eighty-one".