21357645 has 8 divisors (see below), whose sum is σ = 34172256. Its totient is φ = 11390736.

The previous prime is 21357619. The next prime is 21357697. The reversal of 21357645 is 54675312.

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

It is not a de Polignac number, because 21357645 - 2⁷ = 21357517 is a prime.

It is a super-3 number, since 3×21357645³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 711907 + ... + 711936.

It is an arithmetic number, because the mean of its divisors is an integer number (4271532).

Almost surely, 2^21357645 is an apocalyptic number.

It is an amenable number.

21357645 is a deficient number, since it is larger than the sum of its proper divisors (12814611).

21357645 is a wasteful number, since it uses less digits than its factorization.

21357645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1423851.

The product of its digits is 25200, while the sum is 33.

The square root of 21357645 is about 4621.4332192514. The cubic root of 21357645 is about 277.4498245456.

The spelling of 21357645 in words is "twenty-one million, three hundred fifty-seven thousand, six hundred forty-five".