21722388 has 12 divisors (see below), whose sum is σ = 50685600. Its totient is φ = 7240792.

The previous prime is 21722387. The next prime is 21722423. The reversal of 21722388 is 88322712.

It is a tau number, because it is divible by the number of its divisors (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21722381) 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, 905088 + ... + 905111.

It is an arithmetic number, because the mean of its divisors is an integer number (4223800).

Almost surely, 2^21722388 is an apocalyptic number.

It is an amenable number.

21722388 is an abundant number, since it is smaller than the sum of its proper divisors (28963212).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21722388 is a wasteful number, since it uses less digits than its factorization.

21722388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1810206 (or 1810204 counting only the distinct ones).

The product of its digits is 10752, while the sum is 33.

The square root of 21722388 is about 4660.7282692729. The cubic root of 21722388 is about 279.0203348445.

It can be divided in two parts, 2172 and 2388, that added together give a triangular number (4560 = T₉₅).

The spelling of 21722388 in words is "twenty-one million, seven hundred twenty-two thousand, three hundred eighty-eight".