78222521 has 4 divisors (see below), whose sum is σ = 84239652. Its totient is φ = 72205392.

The previous prime is 78222511. The next prime is 78222539. The reversal of 78222521 is 12522287.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12522287 = 29 ⋅431803.

It can be written as a sum of positive squares in 2 ways, for example, as 29376400 + 48846121 = 5420^2 + 6989^2 .

It is a cyclic number.

It is not a de Polignac number, because 78222521 - 2²⁶ = 11113657 is a prime.

It is a super-2 number, since 2×78222521² = 12237525583190882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78222511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3008546 + ... + 3008571.

It is an arithmetic number, because the mean of its divisors is an integer number (21059913).

Almost surely, 2^78222521 is an apocalyptic number.

It is an amenable number.

78222521 is a deficient number, since it is larger than the sum of its proper divisors (6017131).

78222521 is a wasteful number, since it uses less digits than its factorization.

78222521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6017130.

The product of its digits is 4480, while the sum is 29.

The square root of 78222521 is about 8844.3496651817. The cubic root of 78222521 is about 427.6717885101.

The spelling of 78222521 in words is "seventy-eight million, two hundred twenty-two thousand, five hundred twenty-one".