21573730 has 16 divisors (see below), whose sum is σ = 38889144. Its totient is φ = 8616960.

The previous prime is 21573719. The next prime is 21573751. The reversal of 21573730 is 3737512.

It can be written as a sum of positive squares in 4 ways, for example, as 10478169 + 11095561 = 3237^2 + 3331^2 .

It is a super-2 number, since 2×21573730² = 930851652225800, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9154 + ... + 11266.

Almost surely, 2^21573730 is an apocalyptic number.

21573730 is a deficient number, since it is larger than the sum of its proper divisors (17315414).

21573730 is a wasteful number, since it uses less digits than its factorization.

21573730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3141.

The product of its (nonzero) digits is 4410, while the sum is 28.

The square root of 21573730 is about 4644.7529536026. The cubic root of 21573730 is about 278.3823818645.

The spelling of 21573730 in words is "twenty-one million, five hundred seventy-three thousand, seven hundred thirty".