21634642 has 8 divisors (see below), whose sum is σ = 34360956. Its totient is φ = 10180992.

The previous prime is 21634637. The next prime is 21634649. The reversal of 21634642 is 24643612.

It can be written as a sum of positive squares in 2 ways, for example, as 21261321 + 373321 = 4611^2 + 611^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21634642.

It is not an unprimeable number, because it can be changed into a prime (21634649) 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, 318123 + ... + 318190.

Almost surely, 2^21634642 is an apocalyptic number.

21634642 is a deficient number, since it is larger than the sum of its proper divisors (12726314).

21634642 is a wasteful number, since it uses less digits than its factorization.

21634642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 636332.

The product of its digits is 6912, while the sum is 28.

The square root of 21634642 is about 4651.3054081623. The cubic root of 21634642 is about 278.6441337544.

The spelling of 21634642 in words is "twenty-one million, six hundred thirty-four thousand, six hundred forty-two".