21601751 has 4 divisors (see below), whose sum is σ = 21618072. Its totient is φ = 21585432.

The previous prime is 21601721. The next prime is 21601757. The reversal of 21601751 is 15710612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21601751 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21601757) 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, 5981 + ... + 8886.

It is an arithmetic number, because the mean of its divisors is an integer number (5404518).

Almost surely, 2^21601751 is an apocalyptic number.

21601751 is a deficient number, since it is larger than the sum of its proper divisors (16321).

21601751 is a wasteful number, since it uses less digits than its factorization.

21601751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16320.

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21601751 is about 4647.7683892380. The cubic root of 21601751 is about 278.5028552042.

The spelling of 21601751 in words is "twenty-one million, six hundred one thousand, seven hundred fifty-one".