156778778209 has 3 divisors (see below), whose sum is σ = 156779174163. Its totient is φ = 156778382256.

The previous prime is 156778778203. The next prime is 156778778251. The reversal of 156778778209 is 902877877651.

The square root of 156778778209 is 395953.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 902877877651 = 29 ⋅31133719919.

It can be written as a sum of positive squares in only one way, i.e., 32683216225 + 124095561984 = 180785^2 + 352272^2 .

It is not a de Polignac number, because 156778778209 - 2⁷ = 156778778081 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (156778778203) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 197977 + ... + 593929.

It is an arithmetic number, because the mean of its divisors is an integer number (52259724721).

Almost surely, 2^156778778209 is an apocalyptic number.

156778778209 is the 395953-rd square number.

156778778209 is the 197977-th centered octagonal number.

It is an amenable number.

156778778209 is a deficient number, since it is larger than the sum of its proper divisors (395954).

156778778209 is an frugal number, since it uses more digits than its factorization.

156778778209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 791906 (or 395953 counting only the distinct ones).

The product of its (nonzero) digits is 82978560, while the sum is 67.

The spelling of 156778778209 in words is "one hundred fifty-six billion, seven hundred seventy-eight million, seven hundred seventy-eight thousand, two hundred nine".