78499721 has 2 divisors, whose sum is σ = 78499722. Its totient is φ = 78499720.

The previous prime is 78499717. The next prime is 78499753. The reversal of 78499721 is 12799487.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78499600 + 121 = 8860^2 + 11^2 .

It is a cyclic number.

It is not a de Polignac number, because 78499721 - 2² = 78499717 is a prime.

It is not a weakly prime, because it can be changed into another prime (78499021) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39249860 + 39249861.

It is an arithmetic number, because the mean of its divisors is an integer number (39249861).

Almost surely, 2^78499721 is an apocalyptic number.

It is an amenable number.

78499721 is a deficient number, since it is larger than the sum of its proper divisors (1).

78499721 is an equidigital number, since it uses as much as digits as its factorization.

78499721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 254016, while the sum is 47.

The square root of 78499721 is about 8860.0068284398. The cubic root of 78499721 is about 428.1763783048.

The spelling of 78499721 in words is "seventy-eight million, four hundred ninety-nine thousand, seven hundred twenty-one".