21321651 has 8 divisors (see below), whose sum is σ = 30615760. Its totient is φ = 13120992.

The previous prime is 21321647. The next prime is 21321661. The reversal of 21321651 is 15612312.

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

It is not a de Polignac number, because 21321651 - 2² = 21321647 is a prime.

It is a super-2 number, since 2×21321651² = 909225602731602, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21321661) 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, 273316 + ... + 273393.

It is an arithmetic number, because the mean of its divisors is an integer number (3826970).

Almost surely, 2^21321651 is an apocalyptic number.

21321651 is a deficient number, since it is larger than the sum of its proper divisors (9294109).

21321651 is a wasteful number, since it uses less digits than its factorization.

21321651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 546725.

The product of its digits is 360, while the sum is 21.

The square root of 21321651 is about 4617.5373306558. The cubic root of 21321651 is about 277.2938750119.

Adding to 21321651 its reverse (15612312), we get a palindrome (36933963).

The spelling of 21321651 in words is "twenty-one million, three hundred twenty-one thousand, six hundred fifty-one".