21642290 has 8 divisors (see below), whose sum is σ = 38956140. Its totient is φ = 8656912.

The previous prime is 21642289. The next prime is 21642307. The reversal of 21642290 is 9224612.

It can be written as a sum of positive squares in 2 ways, for example, as 21003889 + 638401 = 4583^2 + 799^2 .

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

It is a Curzon number.

It is an unprimeable number.

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, 1082105 + ... + 1082124.

Almost surely, 2^21642290 is an apocalyptic number.

21642290 is a deficient number, since it is larger than the sum of its proper divisors (17313850).

21642290 is a wasteful number, since it uses less digits than its factorization.

21642290 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2164236.

The product of its (nonzero) digits is 1728, while the sum is 26.

The square root of 21642290 is about 4652.1274703086. The cubic root of 21642290 is about 278.6769641146.

The spelling of 21642290 in words is "twenty-one million, six hundred forty-two thousand, two hundred ninety".