78721637 has 2 divisors, whose sum is σ = 78721638. Its totient is φ = 78721636.

The previous prime is 78721633. The next prime is 78721639. The reversal of 78721637 is 73612787.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 55815841 + 22905796 = 7471^2 + 4786^2 .

It is a cyclic number.

It is not a de Polignac number, because 78721637 - 2² = 78721633 is a prime.

It is a super-2 number, since 2×78721637² = 12394192263919538, which contains 22 as substring.

Together with 78721639, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 78721594 and 78721603.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78721633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39360818 + 39360819.

It is an arithmetic number, because the mean of its divisors is an integer number (39360819).

Almost surely, 2^78721637 is an apocalyptic number.

It is an amenable number.

78721637 is a deficient number, since it is larger than the sum of its proper divisors (1).

78721637 is an equidigital number, since it uses as much as digits as its factorization.

78721637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 98784, while the sum is 41.

The square root of 78721637 is about 8872.5214567224. The cubic root of 78721637 is about 428.5794786372.

The spelling of 78721637 in words is "seventy-eight million, seven hundred twenty-one thousand, six hundred thirty-seven".