21751730 has 128 divisors (see below), whose sum is σ = 54867456. Its totient is φ = 5990400.

The previous prime is 21751729. The next prime is 21751753. The reversal of 21751730 is 3715712.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21751730.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 410384 + ... + 410436.

It is an arithmetic number, because the mean of its divisors is an integer number (428652).

Almost surely, 2^21751730 is an apocalyptic number.

21751730 is an abundant number, since it is smaller than the sum of its proper divisors (33115726).

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

21751730 is a wasteful number, since it uses less digits than its factorization.

21751730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 21751730 is about 4663.8749983249. The cubic root of 21751730 is about 279.1459093004.

The spelling of 21751730 in words is "twenty-one million, seven hundred fifty-one thousand, seven hundred thirty".