78021890 has 16 divisors (see below), whose sum is σ = 145282680. Its totient is φ = 30132480.

The previous prime is 78021887. The next prime is 78021941. The reversal of 78021890 is 9812087.

It is a happy number.

It is a Cunningham number, because it is equal to 8833²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 40921609 + 37100281 = 6397^2 + 6091^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 78021890.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 134231 + ... + 134810.

Almost surely, 2^78021890 is an apocalyptic number.

78021890 is a deficient number, since it is larger than the sum of its proper divisors (67260790).

78021890 is a wasteful number, since it uses less digits than its factorization.

78021890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 269077.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 78021890 is about 8833.0000566059. Note that the first 4 decimals coincide. The cubic root of 78021890 is about 427.3058338752.

The spelling of 78021890 in words is "seventy-eight million, twenty-one thousand, eight hundred ninety".