78613821 has 60 divisors (see below), whose sum is σ = 139236636. Its totient is φ = 43908480.

The previous prime is 78613817. The next prime is 78613837. The reversal of 78613821 is 12831687.

It can be written as a sum of positive squares in 2 ways, for example, as 6125625 + 72488196 = 2475^2 + 8514^2 .

It is not a de Polignac number, because 78613821 - 2² = 78613817 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78613841) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 127105 + ... + 127721.

Almost surely, 2^78613821 is an apocalyptic number.

It is an amenable number.

78613821 is a deficient number, since it is larger than the sum of its proper divisors (60622815).

78613821 is a wasteful number, since it uses less digits than its factorization.

78613821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 664 (or 644 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 78613821 is about 8866.4435372927. The cubic root of 78613821 is about 428.3837305217.

The spelling of 78613821 in words is "seventy-eight million, six hundred thirteen thousand, eight hundred twenty-one".