21738961 has 4 divisors (see below), whose sum is σ = 21963172. Its totient is φ = 21514752.

The previous prime is 21738949. The next prime is 21738989. The reversal of 21738961 is 16983712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 11696400 + 10042561 = 3420^2 + 3169^2 .

It is a cyclic number.

It is not a de Polignac number, because 21738961 - 2⁵ = 21738929 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21738961.

It is not an unprimeable number, because it can be changed into a prime (21738901) 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, 111960 + ... + 112153.

It is an arithmetic number, because the mean of its divisors is an integer number (5490793).

Almost surely, 2^21738961 is an apocalyptic number.

It is an amenable number.

21738961 is a deficient number, since it is larger than the sum of its proper divisors (224211).

21738961 is an equidigital number, since it uses as much as digits as its factorization.

21738961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224210.

The product of its digits is 18144, while the sum is 37.

The square root of 21738961 is about 4662.5058713100. The cubic root of 21738961 is about 279.0912759169.

The spelling of 21738961 in words is "twenty-one million, seven hundred thirty-eight thousand, nine hundred sixty-one".