21291039 has 96 divisors (see below), whose sum is σ = 42560000. Its totient is φ = 10478160.

The previous prime is 21291029. The next prime is 21291091. The reversal of 21291039 is 93019212.

It is not a de Polignac number, because 21291039 - 2⁵ = 21291007 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21291019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1120572 + ... + 1120590.

Almost surely, 2^21291039 is an apocalyptic number.

21291039 is a deficient number, since it is larger than the sum of its proper divisors (21268961).

21291039 is a wasteful number, since it uses less digits than its factorization.

21291039 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 71 (or 40 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21291039 is about 4614.2213861062. The cubic root of 21291039 is about 277.1611056540.

The spelling of 21291039 in words is "twenty-one million, two hundred ninety-one thousand, thirty-nine".