78221537 has 4 divisors (see below), whose sum is σ = 82338480. Its totient is φ = 74104596.

The previous prime is 78221519. The next prime is 78221543. The reversal of 78221537 is 73512287.

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 78221537 - 2⁸ = 78221281 is a prime.

It is a super-2 number, since 2×78221537² = 12237217701284738, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 78221497 and 78221506.

It is not an unprimeable number, because it can be changed into a prime (78221557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2058443 + ... + 2058480.

It is an arithmetic number, because the mean of its divisors is an integer number (20584620).

Almost surely, 2^78221537 is an apocalyptic number.

It is an amenable number.

78221537 is a deficient number, since it is larger than the sum of its proper divisors (4116943).

78221537 is a wasteful number, since it uses less digits than its factorization.

78221537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4116942.

The product of its digits is 23520, while the sum is 35.

The square root of 78221537 is about 8844.2940362699. The cubic root of 78221537 is about 427.6699952039.

The spelling of 78221537 in words is "seventy-eight million, two hundred twenty-one thousand, five hundred thirty-seven".