21291040 has 24 divisors (see below), whose sum is σ = 50300460. Its totient is φ = 8516352.

The previous prime is 21291029. The next prime is 21291091. The reversal of 21291040 is 4019212.

It can be written as a sum of positive squares in 2 ways, for example, as 20466576 + 824464 = 4524^2 + 908^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21290999 and 21291017.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66375 + ... + 66694.

Almost surely, 2^21291040 is an apocalyptic number.

21291040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21291040 is an abundant number, since it is smaller than the sum of its proper divisors (29009420).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21291040 is a wasteful number, since it uses less digits than its factorization.

21291040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133084 (or 133076 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21291040 is about 4614.2214944669. The cubic root of 21291040 is about 277.1611099933.

The spelling of 21291040 in words is "twenty-one million, two hundred ninety-one thousand, forty".