78281521 has 4 divisors (see below), whose sum is σ = 79013232. Its totient is φ = 77549812.

The previous prime is 78281519. The next prime is 78281537. The reversal of 78281521 is 12518287.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 78281521 - 2¹ = 78281519 is a prime.

It is a super-2 number, since 2×78281521² = 12255993060146882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (78281221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 365695 + ... + 365908.

It is an arithmetic number, because the mean of its divisors is an integer number (19753308).

Almost surely, 2^78281521 is an apocalyptic number.

It is an amenable number.

78281521 is a deficient number, since it is larger than the sum of its proper divisors (731711).

78281521 is a wasteful number, since it uses less digits than its factorization.

78281521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 731710.

The product of its digits is 8960, while the sum is 34.

The square root of 78281521 is about 8847.6844993478. The cubic root of 78281521 is about 427.7792865123.

The spelling of 78281521 in words is "seventy-eight million, two hundred eighty-one thousand, five hundred twenty-one".