13778866 has 4 divisors (see below), whose sum is σ = 20668302. Its totient is φ = 6889432.

The previous prime is 13778861. The next prime is 13778867. The reversal of 13778866 is 66887731.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 66887731 = 1949 ⋅34319.

It can be written as a sum of positive squares in only one way, i.e., 10374841 + 3404025 = 3221^2 + 1845^2 .

It is not an unprimeable number, because it can be changed into a prime (13778861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3444715 + ... + 3444718.

Almost surely, 2^13778866 is an apocalyptic number.

13778866 is a deficient number, since it is larger than the sum of its proper divisors (6889436).

13778866 is an equidigital number, since it uses as much as digits as its factorization.

13778866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6889435.

The product of its digits is 338688, while the sum is 46.

The square root of 13778866 is about 3711.9894935196. The cubic root of 13778866 is about 239.7385230981.

It can be divided in two parts, 137 and 78866, that added together give a triangular number (79003 = T₃₉₇).

The spelling of 13778866 in words is "thirteen million, seven hundred seventy-eight thousand, eight hundred sixty-six".