21099969 has 12 divisors (see below), whose sum is σ = 33248592. Its totient is φ = 12787800.

The previous prime is 21099959. The next prime is 21099973. The reversal of 21099969 is 96999012.

It is a happy number.

It is not a de Polignac number, because 21099969 - 2¹⁵ = 21067201 is a prime.

It is a super-2 number, since 2×21099969² = 890417383601922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21099959) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 106467 + ... + 106664.

It is an arithmetic number, because the mean of its divisors is an integer number (2770716).

Almost surely, 2^21099969 is an apocalyptic number.

It is an amenable number.

21099969 is a deficient number, since it is larger than the sum of its proper divisors (12148623).

21099969 is a wasteful number, since it uses less digits than its factorization.

21099969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213148 (or 213145 counting only the distinct ones).

The product of its (nonzero) digits is 78732, while the sum is 45.

The square root of 21099969 is about 4593.4702567884. The cubic root of 21099969 is about 276.3295134981.

The spelling of 21099969 in words is "twenty-one million, ninety-nine thousand, nine hundred sixty-nine".