21656242 has 4 divisors (see below), whose sum is σ = 32484366. Its totient is φ = 10828120.

The previous prime is 21656233. The next prime is 21656251. The reversal of 21656242 is 24265612.

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

It is an interprime number because it is at equal distance from previous prime (21656233) and next prime (21656251).

It can be written as a sum of positive squares in only one way, i.e., 19527561 + 2128681 = 4419^2 + 1459^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21656242.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5414059 + ... + 5414062.

Almost surely, 2^21656242 is an apocalyptic number.

21656242 is a deficient number, since it is larger than the sum of its proper divisors (10828124).

21656242 is a wasteful number, since it uses less digits than its factorization.

21656242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10828123.

The product of its digits is 5760, while the sum is 28.

The square root of 21656242 is about 4653.6267577020. The cubic root of 21656242 is about 278.7368355638.

The spelling of 21656242 in words is "twenty-one million, six hundred fifty-six thousand, two hundred forty-two".