21129291 has 12 divisors (see below), whose sum is σ = 30608032. Its totient is φ = 14045616.

The previous prime is 21129289. The next prime is 21129293. The reversal of 21129291 is 19292112.

It is an interprime number because it is at equal distance from previous prime (21129289) and next prime (21129293).

It is not a de Polignac number, because 21129291 - 2¹ = 21129289 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21129293) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 105 + ... + 6501.

Almost surely, 2^21129291 is an apocalyptic number.

21129291 is a deficient number, since it is larger than the sum of its proper divisors (9478741).

21129291 is a wasteful number, since it uses less digits than its factorization.

21129291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6770 (or 6767 counting only the distinct ones).

The product of its digits is 648, while the sum is 27.

The square root of 21129291 is about 4596.6608532716. The cubic root of 21129291 is about 276.4574565550.

The spelling of 21129291 in words is "twenty-one million, one hundred twenty-nine thousand, two hundred ninety-one".