21221642 has 8 divisors (see below), whose sum is σ = 34281156. Its totient is φ = 9794592.

The previous prime is 21221633. The next prime is 21221653. The reversal of 21221642 is 24612212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21169201 + 52441 = 4601^2 + 229^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 408083 + ... + 408134.

Almost surely, 2^21221642 is an apocalyptic number.

21221642 is a deficient number, since it is larger than the sum of its proper divisors (13059514).

21221642 is a wasteful number, since it uses less digits than its factorization.

21221642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816232.

The product of its digits is 384, while the sum is 20.

The square root of 21221642 is about 4606.6953448215. The cubic root of 21221642 is about 276.8596472998.

Adding to 21221642 its reverse (24612212), we get a palindrome (45833854).

The spelling of 21221642 in words is "twenty-one million, two hundred twenty-one thousand, six hundred forty-two".