77821493 has 4 divisors (see below), whose sum is σ = 78251628. Its totient is φ = 77391360.

The previous prime is 77821487. The next prime is 77821553. The reversal of 77821493 is 39412877.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 39412877 = 7 ⋅5630411.

It can be written as a sum of positive squares in 2 ways, for example, as 14730244 + 63091249 = 3838^2 + 7943^2 .

It is a cyclic number.

It is not a de Polignac number, because 77821493 - 2⁴ = 77821477 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 77821493.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77821423) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 214796 + ... + 215157.

It is an arithmetic number, because the mean of its divisors is an integer number (19562907).

Almost surely, 2^77821493 is an apocalyptic number.

It is an amenable number.

77821493 is a deficient number, since it is larger than the sum of its proper divisors (430135).

77821493 is a wasteful number, since it uses less digits than its factorization.

77821493 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 430134.

The product of its digits is 84672, while the sum is 41.

The square root of 77821493 is about 8821.6491088685. The cubic root of 77821493 is about 426.9396792596.

The spelling of 77821493 in words is "seventy-seven million, eight hundred twenty-one thousand, four hundred ninety-three".