21621601 has 8 divisors (see below), whose sum is σ = 23494400. Its totient is φ = 19822320.

The previous prime is 21621577. The next prime is 21621629. The reversal of 21621601 is 10612612.

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

It is not a de Polignac number, because 21621601 - 2¹¹ = 21619553 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621631) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 17766 + ... + 18943.

It is an arithmetic number, because the mean of its divisors is an integer number (2936800).

Almost surely, 2^21621601 is an apocalyptic number.

21621601 is the 2080-th centered decagonal number.

It is an amenable number.

21621601 is a deficient number, since it is larger than the sum of its proper divisors (1872799).

21621601 is a wasteful number, since it uses less digits than its factorization.

21621601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36759.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21621601 is about 4649.9033323285. The cubic root of 21621601 is about 278.5881351616.

It can be divided in two parts, 21621 and 601, that added together give a palindrome (22222).

The spelling of 21621601 in words is "twenty-one million, six hundred twenty-one thousand, six hundred one".