21742215 has 16 divisors (see below), whose sum is σ = 37950336. Its totient is φ = 10541600.

The previous prime is 21742211. The next prime is 21742223. The reversal of 21742215 is 51224712.

It is not a de Polignac number, because 21742215 - 2² = 21742211 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21742211) 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, 65721 + ... + 66050.

It is an arithmetic number, because the mean of its divisors is an integer number (2371896).

Almost surely, 2^21742215 is an apocalyptic number.

21742215 is a deficient number, since it is larger than the sum of its proper divisors (16208121).

21742215 is a wasteful number, since it uses less digits than its factorization.

21742215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131790.

The product of its digits is 1120, while the sum is 24.

The square root of 21742215 is about 4662.8548122368. The cubic root of 21742215 is about 279.1052004969.

Adding to 21742215 its reverse (51224712), we get a palindrome (72966927).

The spelling of 21742215 in words is "twenty-one million, seven hundred forty-two thousand, two hundred fifteen".