78215881 has 2 divisors, whose sum is σ = 78215882. Its totient is φ = 78215880.

The previous prime is 78215873. The next prime is 78215897. The reversal of 78215881 is 18851287.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 69572281 + 8643600 = 8341^2 + 2940^2 .

It is a cyclic number.

It is not a de Polignac number, because 78215881 - 2³ = 78215873 is a prime.

It is a super-2 number, since 2×78215881² = 12235448081212322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (78215281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39107940 + 39107941.

It is an arithmetic number, because the mean of its divisors is an integer number (39107941).

Almost surely, 2^78215881 is an apocalyptic number.

It is an amenable number.

78215881 is a deficient number, since it is larger than the sum of its proper divisors (1).

78215881 is an equidigital number, since it uses as much as digits as its factorization.

78215881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 35840, while the sum is 40.

The square root of 78215881 is about 8843.9742763081. The cubic root of 78215881 is about 427.6596870462.

The spelling of 78215881 in words is "seventy-eight million, two hundred fifteen thousand, eight hundred eighty-one".