78121681 has 8 divisors (see below), whose sum is σ = 90237024. Its totient is φ = 66841920.

The previous prime is 78121657. The next prime is 78121697. The reversal of 78121681 is 18612187.

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 78121681 - 2⁵ = 78121649 is a prime.

It is a super-2 number, since 2×78121681² = 12205994084531522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78121601) 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, 208695 + ... + 209068.

It is an arithmetic number, because the mean of its divisors is an integer number (11279628).

Almost surely, 2^78121681 is an apocalyptic number.

It is an amenable number.

78121681 is a deficient number, since it is larger than the sum of its proper divisors (12115343).

78121681 is a wasteful number, since it uses less digits than its factorization.

78121681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 417791.

The product of its digits is 5376, while the sum is 34.

The square root of 78121681 is about 8838.6470118452. The cubic root of 78121681 is about 427.4879328126.

The spelling of 78121681 in words is "seventy-eight million, one hundred twenty-one thousand, six hundred eighty-one".