21909738 has 8 divisors (see below), whose sum is σ = 43819488. Its totient is φ = 7303244.

The previous prime is 21909733. The next prime is 21909743. The reversal of 21909738 is 83790912.

It is an interprime number because it is at equal distance from previous prime (21909733) and next prime (21909743).

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

21909738 is an admirable number.

It is a junction number, because it is equal to n+sod(n) for n = 21909696 and 21909705.

It is not an unprimeable number, because it can be changed into a prime (21909733) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1825806 + ... + 1825817.

It is an arithmetic number, because the mean of its divisors is an integer number (5477436).

Almost surely, 2^21909738 is an apocalyptic number.

21909738 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21909738 is a wasteful number, since it uses less digits than its factorization.

21909738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3651628.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21909738 is about 4680.7839087059. The cubic root of 21909738 is about 279.8201991922.

The spelling of 21909738 in words is "twenty-one million, nine hundred nine thousand, seven hundred thirty-eight".