21974561 has 12 divisors (see below), whose sum is σ = 25486272. Its totient is φ = 18559944.

The previous prime is 21974551. The next prime is 21974573. The reversal of 21974561 is 16547912.

It is a de Polignac number, because none of the positive numbers 2^k-21974561 is a prime.

It is a super-3 number, since 3×21974561³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21974501) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43436 + ... + 43938.

It is an arithmetic number, because the mean of its divisors is an integer number (2123856).

Almost surely, 2^21974561 is an apocalyptic number.

It is an amenable number.

21974561 is a deficient number, since it is larger than the sum of its proper divisors (3511711).

21974561 is an frugal number, since it uses more digits than its factorization.

21974561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 668 (or 589 counting only the distinct ones).

The product of its digits is 15120, while the sum is 35.

The square root of 21974561 is about 4687.7031689304. The cubic root of 21974561 is about 280.0958897766.

The spelling of 21974561 in words is "twenty-one million, nine hundred seventy-four thousand, five hundred sixty-one".