21291229 has 4 divisors (see below), whose sum is σ = 22411840. Its totient is φ = 20170620.

The previous prime is 21291217. The next prime is 21291239. The reversal of 21291229 is 92219212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21291229 - 2⁵ = 21291197 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21291197 and 21291206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21291239) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 560277 + ... + 560314.

It is an arithmetic number, because the mean of its divisors is an integer number (5602960).

Almost surely, 2^21291229 is an apocalyptic number.

It is an amenable number.

21291229 is a deficient number, since it is larger than the sum of its proper divisors (1120611).

21291229 is a wasteful number, since it uses less digits than its factorization.

21291229 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1120610.

The product of its digits is 1296, while the sum is 28.

The square root of 21291229 is about 4614.2419745826. The cubic root of 21291229 is about 277.1619301081.

The spelling of 21291229 in words is "twenty-one million, two hundred ninety-one thousand, two hundred twenty-nine".