21081142 has 4 divisors (see below), whose sum is σ = 31621716. Its totient is φ = 10540570.

The previous prime is 21081131. The next prime is 21081143. The reversal of 21081142 is 24118012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081143) 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 as a sum of consecutive naturals, namely, 5270284 + ... + 5270287.

It is an arithmetic number, because the mean of its divisors is an integer number (7905429).

Almost surely, 2^21081142 is an apocalyptic number.

21081142 is a deficient number, since it is larger than the sum of its proper divisors (10540574).

21081142 is a wasteful number, since it uses less digits than its factorization.

21081142 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10540573.

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 21081142 is about 4591.4204773686. The cubic root of 21081142 is about 276.2473016259.

Adding to 21081142 its reverse (24118012), we get a palindrome (45199154).

The spelling of 21081142 in words is "twenty-one million, eighty-one thousand, one hundred forty-two".