78217221 has 16 divisors (see below), whose sum is σ = 111984768. Its totient is φ = 48384000.

The previous prime is 78217219. The next prime is 78217231. The reversal of 78217221 is 12271287.

It is a happy number.

It is not a de Polignac number, because 78217221 - 2¹ = 78217219 is a prime.

It is a super-2 number, since 2×78217221² = 12235867321925682, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78217231) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7180 + ... + 14421.

It is an arithmetic number, because the mean of its divisors is an integer number (6999048).

Almost surely, 2^78217221 is an apocalyptic number.

78217221 is a gapful number since it is divisible by the number (71) formed by its first and last digit.

It is an amenable number.

78217221 is a deficient number, since it is larger than the sum of its proper divisors (33767547).

78217221 is a wasteful number, since it uses less digits than its factorization.

78217221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21692.

The product of its digits is 3136, while the sum is 30.

The square root of 78217221 is about 8844.0500337798. The cubic root of 78217221 is about 427.6621292643.

The spelling of 78217221 in words is "seventy-eight million, two hundred seventeen thousand, two hundred twenty-one".