21697219 has 4 divisors (see below), whose sum is σ = 22973544. Its totient is φ = 20420896.

The previous prime is 21697217. The next prime is 21697223. The reversal of 21697219 is 91279612.

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

It is a cyclic number.

It is not a de Polignac number, because 21697219 - 2¹ = 21697217 is a prime.

It is a super-2 number, since 2×21697219² = 941538624667922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21697217) 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 3 ways as a sum of consecutive naturals, for example, 638137 + ... + 638170.

It is an arithmetic number, because the mean of its divisors is an integer number (5743386).

Almost surely, 2^21697219 is an apocalyptic number.

21697219 is a deficient number, since it is larger than the sum of its proper divisors (1276325).

21697219 is a wasteful number, since it uses less digits than its factorization.

21697219 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1276324.

The product of its digits is 13608, while the sum is 37.

The square root of 21697219 is about 4658.0273721823. The cubic root of 21697219 is about 278.9125293727.

The spelling of 21697219 in words is "twenty-one million, six hundred ninety-seven thousand, two hundred nineteen".