2157221309 has 4 divisors (see below), whose sum is σ = 2158494204. Its totient is φ = 2155948416.

The previous prime is 2157221293. The next prime is 2157221357. The reversal of 2157221309 is 9031227512.

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 1977580900 + 179640409 = 44470^2 + 13403^2 .

It is a cyclic number.

It is not a de Polignac number, because 2157221309 - 2⁴ = 2157221293 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2157221399) 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, 633902 + ... + 637295.

It is an arithmetic number, because the mean of its divisors is an integer number (539623551).

Almost surely, 2^2157221309 is an apocalyptic number.

It is an amenable number.

2157221309 is a deficient number, since it is larger than the sum of its proper divisors (1272895).

2157221309 is a wasteful number, since it uses less digits than its factorization.

2157221309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1272894.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 2157221309 is about 46445.8965787076. The cubic root of 2157221309 is about 1292.1062698343.

The spelling of 2157221309 in words is "two billion, one hundred fifty-seven million, two hundred twenty-one thousand, three hundred nine".