21293128 has 8 divisors (see below), whose sum is σ = 39924630. Its totient is φ = 10646560.

The previous prime is 21293119. The next prime is 21293131. The reversal of 21293128 is 82139212.

It can be written as a sum of positive squares in only one way, i.e., 16176484 + 5116644 = 4022^2 + 2262^2 .

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

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21293096 and 21293105.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1330813 + ... + 1330828.

Almost surely, 2^21293128 is an apocalyptic number.

It is an amenable number.

21293128 is a deficient number, since it is larger than the sum of its proper divisors (18631502).

21293128 is a wasteful number, since it uses less digits than its factorization.

21293128 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2661647 (or 2661643 counting only the distinct ones).

The product of its digits is 1728, while the sum is 28.

The square root of 21293128 is about 4614.4477459388. The cubic root of 21293128 is about 277.1701700405.

The spelling of 21293128 in words is "twenty-one million, two hundred ninety-three thousand, one hundred twenty-eight".