78212921 has 2 divisors, whose sum is σ = 78212922. Its totient is φ = 78212920.

The previous prime is 78212917. The next prime is 78212929. The reversal of 78212921 is 12921287.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 51998521 + 26214400 = 7211^2 + 5120^2 .

It is a cyclic number.

It is not a de Polignac number, because 78212921 - 2² = 78212917 is a prime.

It is a super-2 number, since 2×78212921² = 12234522022704482, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (78212929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39106460 + 39106461.

It is an arithmetic number, because the mean of its divisors is an integer number (39106461).

Almost surely, 2^78212921 is an apocalyptic number.

It is an amenable number.

78212921 is a deficient number, since it is larger than the sum of its proper divisors (1).

78212921 is an equidigital number, since it uses as much as digits as its factorization.

78212921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4032, while the sum is 32.

The square root of 78212921 is about 8843.8069291454. The cubic root of 78212921 is about 427.6542921971.

The spelling of 78212921 in words is "seventy-eight million, two hundred twelve thousand, nine hundred twenty-one".