78164359605721 has 9 divisors (see below), whose sum is σ = 82494972327861. Its totient is φ = 74050286803164.

The previous prime is 78164359605691. The next prime is 78164359605733. The reversal of 78164359605721 is 12750695346187.

The square root of 78164359605721 is 8841061.

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

It is not a de Polignac number, because 78164359605721 - 2⁷ = 78164359605593 is a prime.

It is a super-2 number, since 2×78164359605721² (a number of 29 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78164359605781) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 167747500 + ... + 168212818.

It is an arithmetic number, because the mean of its divisors is an integer number (9166108036429).

It is a 1-persistent number, because it is pandigital, but 2⋅78164359605721 = 156328719211442 is not.

Almost surely, 2^{78164359605721} is an apocalyptic number.

78164359605721 is the 8841061-st square number.

78164359605721 is the 4420531-st centered octagonal number.

It is an amenable number.

78164359605721 is a deficient number, since it is larger than the sum of its proper divisors (4330612722140).

78164359605721 is an frugal number, since it uses more digits than its factorization.

78164359605721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 930676 (or 465338 counting only the distinct ones).

The product of its (nonzero) digits is 76204800, while the sum is 64.

The spelling of 78164359605721 in words is "seventy-eight trillion, one hundred sixty-four billion, three hundred fifty-nine million, six hundred five thousand, seven hundred twenty-one".