21663741 has 16 divisors (see below), whose sum is σ = 31707648. Its totient is φ = 13047600.

The previous prime is 21663721. The next prime is 21663751. The reversal of 21663741 is 14736612.

It is not a de Polignac number, because 21663741 - 2¹¹ = 21661693 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21663699 and 21663708.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663721) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3546 + ... + 7476.

It is an arithmetic number, because the mean of its divisors is an integer number (1981728).

Almost surely, 2^21663741 is an apocalyptic number.

It is an amenable number.

21663741 is a deficient number, since it is larger than the sum of its proper divisors (10043907).

21663741 is a wasteful number, since it uses less digits than its factorization.

21663741 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4112.

The product of its digits is 6048, while the sum is 30.

The square root of 21663741 is about 4654.4324036342. The cubic root of 21663741 is about 278.7690049849.

The spelling of 21663741 in words is "twenty-one million, six hundred sixty-three thousand, seven hundred forty-one".