21517842 has 16 divisors (see below), whose sum is σ = 45300960. Its totient is φ = 6795072.

The previous prime is 21517819. The next prime is 21517843. The reversal of 21517842 is 24871512.

It is not an unprimeable number, because it can be changed into a prime (21517843) 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, 94263 + ... + 94490.

It is an arithmetic number, because the mean of its divisors is an integer number (2831310).

Almost surely, 2^21517842 is an apocalyptic number.

21517842 is an abundant number, since it is smaller than the sum of its proper divisors (23783118).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21517842 is a wasteful number, since it uses less digits than its factorization.

21517842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 188777.

The product of its digits is 4480, while the sum is 30.

The square root of 21517842 is about 4638.7328010999. The cubic root of 21517842 is about 278.1417854112.

The spelling of 21517842 in words is "twenty-one million, five hundred seventeen thousand, eight hundred forty-two".