11961513778 has 4 divisors (see below), whose sum is σ = 17942270670. Its totient is φ = 5980756888.

The previous prime is 11961513731. The next prime is 11961513841. The reversal of 11961513778 is 87731516911.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87731516911 = 34543 ⋅2539777.

It can be written as a sum of positive squares in only one way, i.e., 8980026169 + 2981487609 = 94763^2 + 54603^2 .

It is a super-2 number, since 2×11961513778² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2990378443 + ... + 2990378446.

Almost surely, 2^11961513778 is an apocalyptic number.

11961513778 is a deficient number, since it is larger than the sum of its proper divisors (5980756892).

11961513778 is an equidigital number, since it uses as much as digits as its factorization.

11961513778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5980756891.

The product of its digits is 317520, while the sum is 49.

The spelling of 11961513778 in words is "eleven billion, nine hundred sixty-one million, five hundred thirteen thousand, seven hundred seventy-eight".