21861252 has 162 divisors, whose sum is σ = 70678062. Its totient is φ = 5878656.

The previous prime is 21861239. The next prime is 21861263. The reversal of 21861252 is 25216812.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20575296 + 1285956 = 4536^2 + 1134^2 .

It is a tau number, because it is divible by the number of its divisors (162).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 1285948 + ... + 1285964.

Almost surely, 2^21861252 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21861252, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35339031).

21861252 is an abundant number, since it is smaller than the sum of its proper divisors (48816810).

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

21861252 is an equidigital number, since it uses as much as digits as its factorization.

21861252 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59 (or 29 counting only the distinct ones).

The product of its digits is 1920, while the sum is 27.

The square root of 21861252 is about 4675.6017794504. The cubic root of 21861252 is about 279.6136337731.

The spelling of 21861252 in words is "twenty-one million, eight hundred sixty-one thousand, two hundred fifty-two".