21881645 has 8 divisors (see below), whose sum is σ = 26369280. Its totient is φ = 17431120.

The previous prime is 21881627. The next prime is 21881647. The reversal of 21881645 is 54618812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21881645 - 2⁶ = 21881581 is a prime.

It is a super-3 number, since 3×21881645³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21881647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7961 + ... + 10350.

It is an arithmetic number, because the mean of its divisors is an integer number (3296160).

Almost surely, 2^21881645 is an apocalyptic number.

It is an amenable number.

21881645 is a deficient number, since it is larger than the sum of its proper divisors (4487635).

21881645 is a wasteful number, since it uses less digits than its factorization.

21881645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18555.

The product of its digits is 15360, while the sum is 35.

The square root of 21881645 is about 4677.7820599083. The cubic root of 21881645 is about 279.7005514649.

The spelling of 21881645 in words is "twenty-one million, eight hundred eighty-one thousand, six hundred forty-five".