78420721515 has 32 divisors (see below), whose sum is σ = 127867610880. Its totient is φ = 41026567296.

The previous prime is 78420721493. The next prime is 78420721531. The reversal of 78420721515 is 51512702487.

It is not a de Polignac number, because 78420721515 - 2⁶ = 78420721451 is a prime.

It is a super-2 number, since 2×78420721515² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5751376 + ... + 5764994.

It is an arithmetic number, because the mean of its divisors is an integer number (3995862840).

Almost surely, 2^78420721515 is an apocalyptic number.

78420721515 is a deficient number, since it is larger than the sum of its proper divisors (49446889365).

78420721515 is a wasteful number, since it uses less digits than its factorization.

78420721515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20923.

The product of its (nonzero) digits is 156800, while the sum is 42.

The spelling of 78420721515 in words is "seventy-eight billion, four hundred twenty million, seven hundred twenty-one thousand, five hundred fifteen".