21649238 has 20 divisors (see below), whose sum is σ = 35272740. Its totient is φ = 9965592.

The previous prime is 21649237. The next prime is 21649247. The reversal of 21649238 is 83294612.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21649198 and 21649207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21649231) 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 9 ways as a sum of consecutive naturals, for example, 56933 + ... + 57311.

It is an arithmetic number, because the mean of its divisors is an integer number (1763637).

Almost surely, 2^21649238 is an apocalyptic number.

21649238 is a deficient number, since it is larger than the sum of its proper divisors (13623502).

21649238 is an frugal number, since it uses more digits than its factorization.

21649238 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 433 (or 394 counting only the distinct ones).

The product of its digits is 20736, while the sum is 35.

The square root of 21649238 is about 4652.8741655024. The cubic root of 21649238 is about 278.7067828996.

The spelling of 21649238 in words is "twenty-one million, six hundred forty-nine thousand, two hundred thirty-eight".