1971778555 has 4 divisors (see below), whose sum is σ = 2366134272. Its totient is φ = 1577422840.

The previous prime is 1971778531. The next prime is 1971778583. The reversal of 1971778555 is 5558771791.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1971778555 - 2⁷ = 1971778427 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1971778496 and 1971778505.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 197177851 + ... + 197177860.

It is an arithmetic number, because the mean of its divisors is an integer number (591533568).

Almost surely, 2^1971778555 is an apocalyptic number.

1971778555 is a deficient number, since it is larger than the sum of its proper divisors (394355717).

1971778555 is an equidigital number, since it uses as much as digits as its factorization.

1971778555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 394355716.

The product of its digits is 3087000, while the sum is 55.

The square root of 1971778555 is about 44404.7132070459. The cubic root of 1971778555 is about 1253.9668232012.

The spelling of 1971778555 in words is "one billion, nine hundred seventy-one million, seven hundred seventy-eight thousand, five hundred fifty-five".