21203172 has 18 divisors (see below), whose sum is σ = 53596998. Its totient is φ = 7067712.

The previous prime is 21203167. The next prime is 21203177. The reversal of 21203172 is 27130212.

It is an interprime number because it is at equal distance from previous prime (21203167) and next prime (21203177).

It can be written as a sum of positive squares in only one way, i.e., 11128896 + 10074276 = 3336^2 + 3174^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a super-3 number, since 3×21203172³ (a number of 23 digits) contains 333 as substring.

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 (21203177) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 294453 + ... + 294524.

It is an arithmetic number, because the mean of its divisors is an integer number (2977611).

Almost surely, 2^21203172 is an apocalyptic number.

It is an amenable number.

21203172 is an abundant number, since it is smaller than the sum of its proper divisors (32393826).

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

21203172 is a wasteful number, since it uses less digits than its factorization.

21203172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 588987 (or 588982 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21203172 is about 4604.6902175934. The cubic root of 21203172 is about 276.7793035023.

Adding to 21203172 its reverse (27130212), we get a palindrome (48333384).

The spelling of 21203172 in words is "twenty-one million, two hundred three thousand, one hundred seventy-two".