21621842 has 16 divisors (see below), whose sum is σ = 36245664. Its totient is φ = 9588000.

The previous prime is 21621823. The next prime is 21621851. The reversal of 21621842 is 24812612.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11084 + ... + 12887.

It is an arithmetic number, because the mean of its divisors is an integer number (2265354).

Almost surely, 2^21621842 is an apocalyptic number.

21621842 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21621842 is a deficient number, since it is larger than the sum of its proper divisors (14623822).

21621842 is a wasteful number, since it uses less digits than its factorization.

21621842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24025.

The product of its digits is 1536, while the sum is 26.

The square root of 21621842 is about 4649.9292467735. The cubic root of 21621842 is about 278.5891702297.

It can be divided in two parts, 2162 and 1842, that added together give a palindrome (4004).

The spelling of 21621842 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred forty-two".