21660542 has 4 divisors (see below), whose sum is σ = 32490816. Its totient is φ = 10830270.

The previous prime is 21660523. The next prime is 21660559. The reversal of 21660542 is 24506612.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5415134 + ... + 5415137.

It is an arithmetic number, because the mean of its divisors is an integer number (8122704).

Almost surely, 2^21660542 is an apocalyptic number.

21660542 is a deficient number, since it is larger than the sum of its proper divisors (10830274).

21660542 is a wasteful number, since it uses less digits than its factorization.

21660542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10830273.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 21660542 is about 4654.0887400220. The cubic root of 21660542 is about 278.7552827328.

The spelling of 21660542 in words is "twenty-one million, six hundred sixty thousand, five hundred forty-two".