21402180 has 36 divisors (see below), whose sum is σ = 64920492. Its totient is φ = 5707200.

The previous prime is 21402163. The next prime is 21402181. The reversal of 21402180 is 8120412.

It can be written as a sum of positive squares in 2 ways, for example, as 7918596 + 13483584 = 2814^2 + 3672^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21402181) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59271 + ... + 59630.

It is an arithmetic number, because the mean of its divisors is an integer number (1803347).

Almost surely, 2^21402180 is an apocalyptic number.

21402180 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21402180 is an abundant number, since it is smaller than the sum of its proper divisors (43518312).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21402180 is a wasteful number, since it uses less digits than its factorization.

21402180 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118916 (or 118911 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21402180 is about 4626.2490205349. The cubic root of 21402180 is about 277.6425369516.

Adding to 21402180 its reverse (8120412), we get a palindrome (29522592).

The spelling of 21402180 in words is "twenty-one million, four hundred two thousand, one hundred eighty".