1978685551 has 8 divisors (see below), whose sum is σ = 1987690320. Its totient is φ = 1969701312.

The previous prime is 1978685521. The next prime is 1978685557. The reversal of 1978685551 is 1555868791.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1978685551 - 2⁹ = 1978685039 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1978685492 and 1978685501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978685557) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 207576 + ... + 216898.

It is an arithmetic number, because the mean of its divisors is an integer number (248461290).

Almost surely, 2^1978685551 is an apocalyptic number.

1978685551 is a deficient number, since it is larger than the sum of its proper divisors (9004769).

1978685551 is an equidigital number, since it uses as much as digits as its factorization.

1978685551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10265.

The product of its digits is 3024000, while the sum is 55.

The square root of 1978685551 is about 44482.4184481914. The cubic root of 1978685551 is about 1255.4293015523.

The spelling of 1978685551 in words is "one billion, nine hundred seventy-eight million, six hundred eighty-five thousand, five hundred fifty-one".