78561021 has 32 divisors (see below), whose sum is σ = 131328000. Its totient is φ = 40582080.

The previous prime is 78561019. The next prime is 78561053. The reversal of 78561021 is 12016587.

It is not a de Polignac number, because 78561021 - 2¹ = 78561019 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 78561021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78561011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 45115 + ... + 46823.

It is an arithmetic number, because the mean of its divisors is an integer number (4104000).

Almost surely, 2^78561021 is an apocalyptic number.

It is an amenable number.

78561021 is a deficient number, since it is larger than the sum of its proper divisors (52766979).

78561021 is a wasteful number, since it uses less digits than its factorization.

78561021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1929.

The product of its (nonzero) digits is 3360, while the sum is 30.

The square root of 78561021 is about 8863.4655186332. The cubic root of 78561021 is about 428.2878028318.

It can be divided in two parts, 785610 and 21, that added together give a triangular number (785631 = T₁₂₅₃).

The spelling of 78561021 in words is "seventy-eight million, five hundred sixty-one thousand, twenty-one".