21142644 has 24 divisors (see below), whose sum is σ = 49438368. Its totient is φ = 7032480.

The previous prime is 21142643. The next prime is 21142663. The reversal of 21142644 is 44624112.

It is a happy number.

It is a super-2 number, since 2×21142644² = 894022790621472, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21142643) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4954 + ... + 8174.

It is an arithmetic number, because the mean of its divisors is an integer number (2059932).

Almost surely, 2^21142644 is an apocalyptic number.

It is an amenable number.

21142644 is an abundant number, since it is smaller than the sum of its proper divisors (28295724).

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

21142644 is a wasteful number, since it uses less digits than its factorization.

21142644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3775 (or 3773 counting only the distinct ones).

The product of its digits is 1536, while the sum is 24.

The square root of 21142644 is about 4598.1130912582. The cubic root of 21142644 is about 276.5156815573.

Adding to 21142644 its reverse (44624112), we get a palindrome (65766756).

The spelling of 21142644 in words is "twenty-one million, one hundred forty-two thousand, six hundred forty-four".