21722164 has 6 divisors (see below), whose sum is σ = 38013794. Its totient is φ = 10861080.

The previous prime is 21722153. The next prime is 21722167. The reversal of 21722164 is 46122712.

It can be written as a sum of positive squares in only one way, i.e., 19448100 + 2274064 = 4410^2 + 1508^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722167) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2715267 + ... + 2715274.

Almost surely, 2^21722164 is an apocalyptic number.

It is an amenable number.

21722164 is a deficient number, since it is larger than the sum of its proper divisors (16291630).

21722164 is a wasteful number, since it uses less digits than its factorization.

21722164 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5430545 (or 5430543 counting only the distinct ones).

The product of its digits is 1344, while the sum is 25.

The square root of 21722164 is about 4660.7042386318. The cubic root of 21722164 is about 279.0193757607.

Adding to 21722164 its reverse (46122712), we get a palindrome (67844876).

The spelling of 21722164 in words is "twenty-one million, seven hundred twenty-two thousand, one hundred sixty-four".