21501331 has 8 divisors (see below), whose sum is σ = 22680720. Its totient is φ = 20326752.

The previous prime is 21501323. The next prime is 21501349. The reversal of 21501331 is 13310512.

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 21501331 - 2³ = 21501323 is a prime.

It is a super-2 number, since 2×21501331² = 924614469543122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21501371) 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, 11541 + ... + 13273.

It is an arithmetic number, because the mean of its divisors is an integer number (2835090).

Almost surely, 2^21501331 is an apocalyptic number.

21501331 is a deficient number, since it is larger than the sum of its proper divisors (1179389).

21501331 is a wasteful number, since it uses less digits than its factorization.

21501331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2405.

The product of its (nonzero) digits is 90, while the sum is 16.

The square root of 21501331 is about 4636.9527709477. The cubic root of 21501331 is about 278.0706262598.

Adding to 21501331 its reverse (13310512), we get a palindrome (34811843).

It can be divided in two parts, 2150 and 1331, that added together give a square (3481 = 59²).

The spelling of 21501331 in words is "twenty-one million, five hundred one thousand, three hundred thirty-one".