78637681748521 has 27 divisors (see below), whose sum is σ = 91736235121527. Its totient is φ = 67212874658160.

The previous prime is 78637681748489. The next prime is 78637681748531. The reversal of 78637681748521 is 12584718673687.

The square root of 78637681748521 is 8867789.

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

It can be written as a sum of positive squares in only one way, i.e., 52700703225625 + 25936978522896 = 7259525^2 + 5092836^2 .

It is not a de Polignac number, because 78637681748521 - 2⁵ = 78637681748489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78637681748531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 24643584036 + ... + 24643587226.

Almost surely, 2^{78637681748521} is an apocalyptic number.

78637681748521 is the 8867789-th square number.

78637681748521 is the 4433895-th centered octagonal number.

It is an amenable number.

78637681748521 is a deficient number, since it is larger than the sum of its proper divisors (13098553373006).

78637681748521 is an frugal number, since it uses more digits than its factorization.

78637681748521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7190 (or 3595 counting only the distinct ones).

The product of its digits is 758661120, while the sum is 73.

The spelling of 78637681748521 in words is "seventy-eight trillion, six hundred thirty-seven billion, six hundred eighty-one million, seven hundred forty-eight thousand, five hundred twenty-one".