21999969 has 6 divisors (see below), whose sum is σ = 31777746. Its totient is φ = 14666640.

The previous prime is 21999917. The next prime is 21999973. The reversal of 21999969 is 96999912.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 11189025 + 10810944 = 3345^2 + 3288^2 .

It is not a de Polignac number, because 21999969 - 2²⁴ = 5222753 is a prime.

It is a super-2 number, since 2×21999969² = 967997272001922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21999269) 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 5 ways as a sum of consecutive naturals, for example, 1222212 + ... + 1222229.

It is an arithmetic number, because the mean of its divisors is an integer number (5296291).

Almost surely, 2^21999969 is an apocalyptic number.

It is an amenable number.

21999969 is a deficient number, since it is larger than the sum of its proper divisors (9777777).

21999969 is a wasteful number, since it uses less digits than its factorization.

21999969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2444447 (or 2444444 counting only the distinct ones).

The product of its digits is 708588, while the sum is 54.

The square root of 21999969 is about 4690.4124552112. The cubic root of 21999969 is about 280.2038014545.

The spelling of 21999969 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred sixty-nine".