13778654465521 has 27 divisors (see below), whose sum is σ = 15438706259403. Its totient is φ = 12287778737520.

The previous prime is 13778654465503. The next prime is 13778654465551. The reversal of 13778654465521 is 12556445687731.

It is a happy number.

The square root of 13778654465521 is 3711961.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 9932992272225 + 3845662193296 = 3151665^2 + 1961036^2 .

It is a de Polignac number, because none of the positive numbers 2^k-13778654465521 is a prime.

It is a Smith number, since the sum of its digits (64) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (13778654465551) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 2164070080 + ... + 2164076446.

Almost surely, 2^{13778654465521} is an apocalyptic number.

13778654465521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

13778654465521 is the 3711961-st square number.

13778654465521 is the 1855981-st centered octagonal number.

It is an amenable number.

13778654465521 is a deficient number, since it is larger than the sum of its proper divisors (1660051793882).

13778654465521 is an frugal number, since it uses more digits than its factorization.

13778654465521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12862 (or 6431 counting only the distinct ones).

The product of its digits is 169344000, while the sum is 64.

Multiplying 13778654465521 by its sum of digits (64), we get a square (881833885793344 = 29695688²).

The spelling of 13778654465521 in words is "thirteen trillion, seven hundred seventy-eight billion, six hundred fifty-four million, four hundred sixty-five thousand, five hundred twenty-one".