21229691 has 6 divisors (see below), whose sum is σ = 24695820. Its totient is φ = 18196836.

The previous prime is 21229679. The next prime is 21229693. The reversal of 21229691 is 19692212.

It is not a de Polignac number, because 21229691 - 2¹⁸ = 20967547 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21229693) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 216581 + ... + 216678.

It is an arithmetic number, because the mean of its divisors is an integer number (4115970).

Almost surely, 2^21229691 is an apocalyptic number.

21229691 is a deficient number, since it is larger than the sum of its proper divisors (3466129).

21229691 is an equidigital number, since it uses as much as digits as its factorization.

21229691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 433273 (or 433266 counting only the distinct ones).

The product of its digits is 3888, while the sum is 32.

The square root of 21229691 is about 4607.5688817423. The cubic root of 21229691 is about 276.8946455596.

The spelling of 21229691 in words is "twenty-one million, two hundred twenty-nine thousand, six hundred ninety-one".