21172140 has 216 divisors, whose sum is σ = 76435632. Its totient is φ = 4700160.

The previous prime is 21172139. The next prime is 21172141. The reversal of 21172140 is 4127112.

It is an interprime number because it is at equal distance from previous prime (21172139) and next prime (21172141).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172141) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 572202 + ... + 572238.

Almost surely, 2^21172140 is an apocalyptic number.

21172140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21172140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38217816).

21172140 is an abundant number, since it is smaller than the sum of its proper divisors (55263492).

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

21172140 is a wasteful number, since it uses less digits than its factorization.

21172140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97 (or 75 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21172140 is about 4601.3193760051. The cubic root of 21172140 is about 276.6442103675.

Adding to 21172140 its reverse (4127112), we get a palindrome (25299252).

It can be divided in two parts, 21172 and 140, that added together give a palindrome (21312).

The spelling of 21172140 in words is "twenty-one million, one hundred seventy-two thousand, one hundred forty".