21905242 has 4 divisors (see below), whose sum is σ = 32857866. Its totient is φ = 10952620.

The previous prime is 21905239. The next prime is 21905263. The reversal of 21905242 is 24250912.

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

It can be written as a sum of positive squares in only one way, i.e., 20985561 + 919681 = 4581^2 + 959^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5476309 + ... + 5476312.

Almost surely, 2^21905242 is an apocalyptic number.

21905242 is a deficient number, since it is larger than the sum of its proper divisors (10952624).

21905242 is a wasteful number, since it uses less digits than its factorization.

21905242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10952623.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 21905242 is about 4680.3036226296. The cubic root of 21905242 is about 279.8010576629.

The spelling of 21905242 in words is "twenty-one million, nine hundred five thousand, two hundred forty-two".