21229091 has 4 divisors (see below), whose sum is σ = 22862112. Its totient is φ = 19596072.

The previous prime is 21229063. The next prime is 21229111. The reversal of 21229091 is 19092212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21229091 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21229091.

It is not an unprimeable number, because it can be changed into a prime (21229001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 816491 + ... + 816516.

It is an arithmetic number, because the mean of its divisors is an integer number (5715528).

Almost surely, 2^21229091 is an apocalyptic number.

21229091 is a deficient number, since it is larger than the sum of its proper divisors (1633021).

21229091 is a wasteful number, since it uses less digits than its factorization.

21229091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1633020.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21229091 is about 4607.5037710240. The cubic root of 21229091 is about 276.8920369748.

The spelling of 21229091 in words is "twenty-one million, two hundred twenty-nine thousand, ninety-one".