78400441621 has 2 divisors, whose sum is σ = 78400441622. Its totient is φ = 78400441620.

The previous prime is 78400441597. The next prime is 78400441681. The reversal of 78400441621 is 12614400487.

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., 66403620721 + 11996820900 = 257689^2 + 109530^2 .

It is a cyclic number.

It is not a de Polignac number, because 78400441621 - 2⁹ = 78400441109 is a prime.

It is a super-2 number, since 2×78400441621² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (78400441681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39200220810 + 39200220811.

It is an arithmetic number, because the mean of its divisors is an integer number (39200220811).

Almost surely, 2^78400441621 is an apocalyptic number.

It is an amenable number.

78400441621 is a deficient number, since it is larger than the sum of its proper divisors (1).

78400441621 is an equidigital number, since it uses as much as digits as its factorization.

78400441621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43008, while the sum is 37.

The spelling of 78400441621 in words is "seventy-eight billion, four hundred million, four hundred forty-one thousand, six hundred twenty-one".