22151221 has 4 divisors (see below), whose sum is σ = 23454252. Its totient is φ = 20848192.

The previous prime is 22151209. The next prime is 22151249. The reversal of 22151221 is 12215122.

It is a happy number.

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 9090225 + 13060996 = 3015^2 + 3614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-22151221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 22151195 and 22151204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22151201) 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, 651490 + ... + 651523.

It is an arithmetic number, because the mean of its divisors is an integer number (5863563).

Almost surely, 2^22151221 is an apocalyptic number.

It is an amenable number.

22151221 is a deficient number, since it is larger than the sum of its proper divisors (1303031).

22151221 is a wasteful number, since it uses less digits than its factorization.

22151221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1303030.

The product of its digits is 80, while the sum is 16.

The square root of 22151221 is about 4706.5083660820. The cubic root of 22151221 is about 280.8444785577.

Adding to 22151221 its reverse (12215122), we get a palindrome (34366343).

The spelling of 22151221 in words is "twenty-two million, one hundred fifty-one thousand, two hundred twenty-one".