78857739721 has 2 divisors, whose sum is σ = 78857739722. Its totient is φ = 78857739720.

The previous prime is 78857739679. The next prime is 78857739743. The reversal of 78857739721 is 12793775887.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73416612025 + 5441127696 = 270955^2 + 73764^2 .

It is a cyclic number.

It is not a de Polignac number, because 78857739721 - 2¹⁷ = 78857608649 is a prime.

It is a super-2 number, since 2×78857739721² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78857769721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39428869860 + 39428869861.

It is an arithmetic number, because the mean of its divisors is an integer number (39428869861).

Almost surely, 2^78857739721 is an apocalyptic number.

It is an amenable number.

78857739721 is a deficient number, since it is larger than the sum of its proper divisors (1).

78857739721 is an equidigital number, since it uses as much as digits as its factorization.

78857739721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41489280, while the sum is 64.

The spelling of 78857739721 in words is "seventy-eight billion, eight hundred fifty-seven million, seven hundred thirty-nine thousand, seven hundred twenty-one".