15644816381 has 2 divisors, whose sum is σ = 15644816382. Its totient is φ = 15644816380.

The previous prime is 15644816357. The next prime is 15644816387. The reversal of 15644816381 is 18361844651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14378168281 + 1266648100 = 119909^2 + 35590^2 .

It is a cyclic number.

It is not a de Polignac number, because 15644816381 - 2²² = 15640622077 is a prime.

It is a super-2 number, since 2×15644816381² (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 (15644816387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7822408190 + 7822408191.

It is an arithmetic number, because the mean of its divisors is an integer number (7822408191).

Almost surely, 2^15644816381 is an apocalyptic number.

It is an amenable number.

15644816381 is a deficient number, since it is larger than the sum of its proper divisors (1).

15644816381 is an equidigital number, since it uses as much as digits as its factorization.

15644816381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 552960, while the sum is 47.

The spelling of 15644816381 in words is "fifteen billion, six hundred forty-four million, eight hundred sixteen thousand, three hundred eighty-one".