21505738 has 8 divisors (see below), whose sum is σ = 32314788. Its totient is φ = 10734144.

The previous prime is 21505721. The next prime is 21505751. The reversal of 21505738 is 83750512.

It can be written as a sum of positive squares in 2 ways, for example, as 21501769 + 3969 = 4637^2 + 63^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7881 + ... + 10252.

Almost surely, 2^21505738 is an apocalyptic number.

21505738 is a deficient number, since it is larger than the sum of its proper divisors (10809050).

21505738 is a wasteful number, since it uses less digits than its factorization.

21505738 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18728.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21505738 is about 4637.4279509228. The cubic root of 21505738 is about 278.0896231231.

The spelling of 21505738 in words is "twenty-one million, five hundred five thousand, seven hundred thirty-eight".