1978511869 has 2 divisors, whose sum is σ = 1978511870. Its totient is φ = 1978511868.

The previous prime is 1978511861. The next prime is 1978511879. The reversal of 1978511869 is 9681158791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1635150969 + 343360900 = 40437^2 + 18530^2 .

It is a cyclic number.

It is not a de Polignac number, because 1978511869 - 2³ = 1978511861 is a prime.

It is a super-2 number, since 2×1978511869² = 7829018431547746322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1978511861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 989255934 + 989255935.

It is an arithmetic number, because the mean of its divisors is an integer number (989255935).

Almost surely, 2^1978511869 is an apocalyptic number.

It is an amenable number.

1978511869 is a deficient number, since it is larger than the sum of its proper divisors (1).

1978511869 is an equidigital number, since it uses as much as digits as its factorization.

1978511869 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1088640, while the sum is 55.

The square root of 1978511869 is about 44480.4661508847. The cubic root of 1978511869 is about 1255.3925681003.

The spelling of 1978511869 in words is "one billion, nine hundred seventy-eight million, five hundred eleven thousand, eight hundred sixty-nine".