21012144 has 20 divisors (see below), whose sum is σ = 54281496. Its totient is φ = 7004032.

The previous prime is 21012137. The next prime is 21012151. The reversal of 21012144 is 44121012.

It is an interprime number because it is at equal distance from previous prime (21012137) and next prime (21012151).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 218829 + ... + 218924.

Almost surely, 2^21012144 is an apocalyptic number.

21012144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21012144 is an abundant number, since it is smaller than the sum of its proper divisors (33269352).

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

21012144 is a wasteful number, since it uses less digits than its factorization.

21012144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 437764 (or 437758 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 21012144 is about 4583.9005224808. The cubic root of 21012144 is about 275.9455889380.

Adding to 21012144 its reverse (44121012), we get a palindrome (65133156).

The spelling of 21012144 in words is "twenty-one million, twelve thousand, one hundred forty-four".