78212621 has 4 divisors (see below), whose sum is σ = 78238044. Its totient is φ = 78187200.

The previous prime is 78212609. The next prime is 78212639. The reversal of 78212621 is 12621287.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 26574025 + 51638596 = 5155^2 + 7186^2 .

It is a cyclic number.

It is not a de Polignac number, because 78212621 - 2¹⁰ = 78211597 is a prime.

It is a super-2 number, since 2×78212621² = 12234428167379282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78212021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7340 + ... + 14501.

It is an arithmetic number, because the mean of its divisors is an integer number (19559511).

Almost surely, 2^78212621 is an apocalyptic number.

It is an amenable number.

78212621 is a deficient number, since it is larger than the sum of its proper divisors (25423).

78212621 is a wasteful number, since it uses less digits than its factorization.

78212621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25422.

The product of its digits is 2688, while the sum is 29.

The square root of 78212621 is about 8843.7899681076. The cubic root of 78212621 is about 427.6537454142.

The spelling of 78212621 in words is "seventy-eight million, two hundred twelve thousand, six hundred twenty-one".