21291128 has 8 divisors (see below), whose sum is σ = 39920880. Its totient is φ = 10645560.

The previous prime is 21291119. The next prime is 21291139. The reversal of 21291128 is 82119212.

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 21291097 and 21291106.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330688 + ... + 1330703.

It is an arithmetic number, because the mean of its divisors is an integer number (4990110).

Almost surely, 2^21291128 is an apocalyptic number.

It is an amenable number.

21291128 is a deficient number, since it is larger than the sum of its proper divisors (18629752).

21291128 is a wasteful number, since it uses less digits than its factorization.

21291128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2661397 (or 2661393 counting only the distinct ones).

The product of its digits is 576, while the sum is 26.

The square root of 21291128 is about 4614.2310301934. The cubic root of 21291128 is about 277.1614918463.

The spelling of 21291128 in words is "twenty-one million, two hundred ninety-one thousand, one hundred twenty-eight".