1978228221 has 4 divisors (see below), whose sum is σ = 2637637632. Its totient is φ = 1318818812.

The previous prime is 1978228211. The next prime is 1978228237. The reversal of 1978228221 is 1228228791.

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 1978228221 - 2⁷ = 1978228093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1978228211) 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, 329704701 + ... + 329704706.

It is an arithmetic number, because the mean of its divisors is an integer number (659409408).

Almost surely, 2^1978228221 is an apocalyptic number.

It is an amenable number.

1978228221 is a deficient number, since it is larger than the sum of its proper divisors (659409411).

1978228221 is an equidigital number, since it uses as much as digits as its factorization.

1978228221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 659409410.

The product of its digits is 64512, while the sum is 42.

The square root of 1978228221 is about 44477.2775808052. The cubic root of 1978228221 is about 1255.3325724010.

The spelling of 1978228221 in words is "one billion, nine hundred seventy-eight million, two hundred twenty-eight thousand, two hundred twenty-one".