21001355 has 8 divisors (see below), whose sum is σ = 25400832. Its totient is φ = 16668288.

The previous prime is 21001349. The next prime is 21001367. The reversal of 21001355 is 55310012.

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

It is a cyclic number.

It is not a de Polignac number, because 21001355 - 2¹⁸ = 20739211 is a prime.

It is a Duffinian number.

21001355 is a modest number, since divided by 1355 gives 210 as remainder.

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, 15902 + ... + 17171.

It is an arithmetic number, because the mean of its divisors is an integer number (3175104).

Almost surely, 2^21001355 is an apocalyptic number.

21001355 is a deficient number, since it is larger than the sum of its proper divisors (4399477).

21001355 is a wasteful number, since it uses less digits than its factorization.

21001355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33205.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21001355 is about 4582.7235351917. The cubic root of 21001355 is about 275.8983513871.

Adding to 21001355 its reverse (55310012), we get a palindrome (76311367).

The spelling of 21001355 in words is "twenty-one million, one thousand, three hundred fifty-five".