21921601 has 8 divisors (see below), whose sum is σ = 23709224. Its totient is φ = 20148480.

The previous prime is 21921577. The next prime is 21921607. The reversal of 21921601 is 10612912.

It can be written as a sum of positive squares in 4 ways, for example, as 1210000 + 20711601 = 1100^2 + 4551^2 .

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21921601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21921607) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 366 + ... + 6631.

It is an arithmetic number, because the mean of its divisors is an integer number (2963653).

Almost surely, 2^21921601 is an apocalyptic number.

It is an amenable number.

21921601 is a deficient number, since it is larger than the sum of its proper divisors (1787623).

21921601 is a wasteful number, since it uses less digits than its factorization.

21921601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7251.

The product of its (nonzero) digits is 216, while the sum is 22.

The square root of 21921601 is about 4682.0509394922. The cubic root of 21921601 is about 279.8706928447.

It can be divided in two parts, 21921 and 601, that added together give a palindrome (22522).

The spelling of 21921601 in words is "twenty-one million, nine hundred twenty-one thousand, six hundred one".