1978688961 has 12 divisors (see below), whose sum is σ = 2858583780. Its totient is φ = 1318905600.

The previous prime is 1978688947. The next prime is 1978688963. The reversal of 1978688961 is 1698868791.

It can be written as a sum of positive squares in 2 ways, for example, as 639128961 + 1339560000 = 25281^2 + 36600^2 .

It is not a de Polignac number, because 1978688961 - 2⁶ = 1978688897 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1978688963) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 53161 + ... + 82361.

It is an arithmetic number, because the mean of its divisors is an integer number (238215315).

Almost surely, 2^1978688961 is an apocalyptic number.

It is an amenable number.

1978688961 is a deficient number, since it is larger than the sum of its proper divisors (879894819).

1978688961 is a wasteful number, since it uses less digits than its factorization.

1978688961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36736 (or 36733 counting only the distinct ones).

The product of its digits is 10450944, while the sum is 63.

The square root of 1978688961 is about 44482.4567779254. The cubic root of 1978688961 is about 1255.4300227400.

It can be divided in two parts, 1978688 and 961, that added together give a square (1979649 = 1407²).

The spelling of 1978688961 in words is "one billion, nine hundred seventy-eight million, six hundred eighty-eight thousand, nine hundred sixty-one".