21661071 has 8 divisors (see below), whose sum is σ = 29277360. Its totient is φ = 14242752.

The previous prime is 21661061. The next prime is 21661097. The reversal of 21661071 is 17016612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21661071 - 2⁹ = 21660559 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661001) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49236 + ... + 49673.

It is an arithmetic number, because the mean of its divisors is an integer number (3659670).

Almost surely, 2^21661071 is an apocalyptic number.

21661071 is a deficient number, since it is larger than the sum of its proper divisors (7616289).

21661071 is an equidigital number, since it uses as much as digits as its factorization.

21661071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98985.

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21661071 is about 4654.1455714234. The cubic root of 21661071 is about 278.7575519950.

Adding to 21661071 its reverse (17016612), we get a palindrome (38677683).

The spelling of 21661071 in words is "twenty-one million, six hundred sixty-one thousand, seventy-one".