21289916 has 12 divisors (see below), whose sum is σ = 39449088. Its totient is φ = 10018752.

The previous prime is 21289913. The next prime is 21289949. The reversal of 21289916 is 61998212.

It is a self number, because there is not a number n which added to its sum of digits gives 21289916.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21289913) 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, 156476 + ... + 156611.

It is an arithmetic number, because the mean of its divisors is an integer number (3287424).

Almost surely, 2^21289916 is an apocalyptic number.

It is an amenable number.

21289916 is a deficient number, since it is larger than the sum of its proper divisors (18159172).

21289916 is a wasteful number, since it uses less digits than its factorization.

21289916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 313108 (or 313106 counting only the distinct ones).

The product of its digits is 15552, while the sum is 38.

The square root of 21289916 is about 4614.0996954986. The cubic root of 21289916 is about 277.1562325962.

The spelling of 21289916 in words is "twenty-one million, two hundred eighty-nine thousand, nine hundred sixteen".