21801015 has 32 divisors (see below), whose sum is σ = 39029760. Its totient is φ = 11545632.

The previous prime is 21801001. The next prime is 21801019. The reversal of 21801015 is 51010812.

It is not a de Polignac number, because 21801015 - 2⁸ = 21800759 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801019) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22062 + ... + 23028.

It is an arithmetic number, because the mean of its divisors is an integer number (1219680).

Almost surely, 2^21801015 is an apocalyptic number.

21801015 is a deficient number, since it is larger than the sum of its proper divisors (17228745).

21801015 is a wasteful number, since it uses less digits than its factorization.

21801015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148 (or 1142 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 21801015 is about 4669.1557052641. The cubic root of 21801015 is about 279.3565795701.

Adding to 21801015 its reverse (51010812), we get a palindrome (72811827).

The spelling of 21801015 in words is "twenty-one million, eight hundred one thousand, fifteen".