21708542 has 4 divisors (see below), whose sum is σ = 32562816. Its totient is φ = 10854270.

The previous prime is 21708539. The next prime is 21708553. The reversal of 21708542 is 24580712.

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

It is a super-3 number, since 3×21708542³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5427134 + ... + 5427137.

It is an arithmetic number, because the mean of its divisors is an integer number (8140704).

Almost surely, 2^21708542 is an apocalyptic number.

21708542 is a deficient number, since it is larger than the sum of its proper divisors (10854274).

21708542 is a wasteful number, since it uses less digits than its factorization.

21708542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10854273.

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 21708542 is about 4659.2426423186. The cubic root of 21708542 is about 278.9610390819.

The spelling of 21708542 in words is "twenty-one million, seven hundred eight thousand, five hundred forty-two".