21881172 has 12 divisors (see below), whose sum is σ = 51056096. Its totient is φ = 7293720.

The previous prime is 21881143. The next prime is 21881177. The reversal of 21881172 is 27118812.

It is a happy number.

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 (21881177) 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, 911704 + ... + 911727.

Almost surely, 2^21881172 is an apocalyptic number.

It is an amenable number.

21881172 is an abundant number, since it is smaller than the sum of its proper divisors (29174924).

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

21881172 is a wasteful number, since it uses less digits than its factorization.

21881172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1823438 (or 1823436 counting only the distinct ones).

The product of its digits is 1792, while the sum is 30.

The square root of 21881172 is about 4677.7315014866. The cubic root of 21881172 is about 279.6985360875.

Adding to 21881172 its reverse (27118812), we get a palindrome (48999984).

The spelling of 21881172 in words is "twenty-one million, eight hundred eighty-one thousand, one hundred seventy-two".