21881606 has 4 divisors (see below), whose sum is σ = 32822412. Its totient is φ = 10940802.

The previous prime is 21881603. The next prime is 21881611. The reversal of 21881606 is 60618812.

It is a semiprime because it is the product of two primes.

It is a super-2 number, since 2×21881606² = 957609362278472, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21881603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5470400 + ... + 5470403.

It is an arithmetic number, because the mean of its divisors is an integer number (8205603).

Almost surely, 2^21881606 is an apocalyptic number.

21881606 is a deficient number, since it is larger than the sum of its proper divisors (10940806).

21881606 is a wasteful number, since it uses less digits than its factorization.

21881606 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10940805.

The product of its (nonzero) digits is 4608, while the sum is 32.

The square root of 21881606 is about 4677.7778912642. Note that the first 3 decimals coincide. The cubic root of 21881606 is about 279.7003852932.

The spelling of 21881606 in words is "twenty-one million, eight hundred eighty-one thousand, six hundred six".