21945287 has 24 divisors (see below), whose sum is σ = 28115136. Its totient is φ = 16970688.

The previous prime is 21945277. The next prime is 21945293. The reversal of 21945287 is 78254912.

It is not a de Polignac number, because 21945287 - 2⁴ = 21945271 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21945287.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21945277) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29573 + ... + 30305.

It is an arithmetic number, because the mean of its divisors is an integer number (1171464).

Almost surely, 2^21945287 is an apocalyptic number.

21945287 is a deficient number, since it is larger than the sum of its proper divisors (6169849).

21945287 is a wasteful number, since it uses less digits than its factorization.

21945287 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 807 (or 800 counting only the distinct ones).

The product of its digits is 40320, while the sum is 38.

The square root of 21945287 is about 4684.5797036661. The cubic root of 21945287 is about 279.9714554235.

The spelling of 21945287 in words is "twenty-one million, nine hundred forty-five thousand, two hundred eighty-seven".