21788242 has 12 divisors (see below), whose sum is σ = 38018430. Its totient is φ = 9337776.

The previous prime is 21788233. The next prime is 21788293. The reversal of 21788242 is 24288712.

It can be written as a sum of positive squares in only one way, i.e., 19263321 + 2524921 = 4389^2 + 1589^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21788198 and 21788207.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 111067 + ... + 111262.

Almost surely, 2^21788242 is an apocalyptic number.

21788242 is a deficient number, since it is larger than the sum of its proper divisors (16230188).

21788242 is a wasteful number, since it uses less digits than its factorization.

21788242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222345 (or 222338 counting only the distinct ones).

The product of its digits is 14336, while the sum is 34.

The square root of 21788242 is about 4667.7876986855. The cubic root of 21788242 is about 279.3020114888.

The spelling of 21788242 in words is "twenty-one million, seven hundred eighty-eight thousand, two hundred forty-two".