21320501 has 4 divisors (see below), whose sum is σ = 21509292. Its totient is φ = 21131712.

The previous prime is 21320491. The next prime is 21320513. The reversal of 21320501 is 10502312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9424900 + 11895601 = 3070^2 + 3449^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320501 - 2¹⁰ = 21319477 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 94226 + ... + 94451.

It is an arithmetic number, because the mean of its divisors is an integer number (5377323).

Almost surely, 2^21320501 is an apocalyptic number.

It is an amenable number.

21320501 is a deficient number, since it is larger than the sum of its proper divisors (188791).

21320501 is a wasteful number, since it uses less digits than its factorization.

21320501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188790.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21320501 is about 4617.4128037246. The cubic root of 21320501 is about 277.2888895679.

Adding to 21320501 its reverse (10502312), we get a palindrome (31822813).

The spelling of 21320501 in words is "twenty-one million, three hundred twenty thousand, five hundred one".