21721654 has 8 divisors (see below), whose sum is σ = 32674320. Its totient is φ = 10830216.

The previous prime is 21721621. The next prime is 21721717. The reversal of 21721654 is 45612712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-3 number, since 3×21721654³ (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 (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14409 + ... + 15844.

It is an arithmetic number, because the mean of its divisors is an integer number (4084290).

Almost surely, 2^21721654 is an apocalyptic number.

21721654 is a deficient number, since it is larger than the sum of its proper divisors (10952666).

21721654 is a wasteful number, since it uses less digits than its factorization.

21721654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30614.

The product of its digits is 3360, while the sum is 28.

The square root of 21721654 is about 4660.6495255490. The cubic root of 21721654 is about 279.0171921079.

The spelling of 21721654 in words is "twenty-one million, seven hundred twenty-one thousand, six hundred fifty-four".