21739869 has 6 divisors (see below), whose sum is σ = 31402046. Its totient is φ = 14493240.

The previous prime is 21739859. The next prime is 21739873. The reversal of 21739869 is 96893712.

It can be written as a sum of positive squares in only one way, i.e., 21734244 + 5625 = 4662^2 + 75^2 .

It is not a de Polignac number, because 21739869 - 2⁷ = 21739741 is a prime.

It is a super-2 number, since 2×21739869² = 945243808274322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21739829) 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, 1207762 + ... + 1207779.

Almost surely, 2^21739869 is an apocalyptic number.

It is an amenable number.

21739869 is a deficient number, since it is larger than the sum of its proper divisors (9662177).

21739869 is a wasteful number, since it uses less digits than its factorization.

21739869 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2415547 (or 2415544 counting only the distinct ones).

The product of its digits is 163296, while the sum is 45.

The square root of 21739869 is about 4662.6032428248. The cubic root of 21739869 is about 279.0951615879.

The spelling of 21739869 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred sixty-nine".