78406421 has 2 divisors, whose sum is σ = 78406422. Its totient is φ = 78406420.

The previous prime is 78406417. The next prime is 78406429. The reversal of 78406421 is 12460487.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77616100 + 790321 = 8810^2 + 889^2 .

It is a cyclic number.

It is not a de Polignac number, because 78406421 - 2² = 78406417 is a prime.

It is a super-2 number, since 2×78406421² = 12295133708058482, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78406429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39203210 + 39203211.

It is an arithmetic number, because the mean of its divisors is an integer number (39203211).

Almost surely, 2^78406421 is an apocalyptic number.

It is an amenable number.

78406421 is a deficient number, since it is larger than the sum of its proper divisors (1).

78406421 is an equidigital number, since it uses as much as digits as its factorization.

78406421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 78406421 is about 8854.7400300630. The cubic root of 78406421 is about 428.0066762431.

The spelling of 78406421 in words is "seventy-eight million, four hundred six thousand, four hundred twenty-one".