21242878 has 4 divisors (see below), whose sum is σ = 31864320. Its totient is φ = 10621438.

The previous prime is 21242873. The next prime is 21242917. The reversal of 21242878 is 87824212.

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 (21242873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5310718 + ... + 5310721.

It is an arithmetic number, because the mean of its divisors is an integer number (7966080).

Almost surely, 2^21242878 is an apocalyptic number.

21242878 is a deficient number, since it is larger than the sum of its proper divisors (10621442).

21242878 is a wasteful number, since it uses less digits than its factorization.

21242878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10621441.

The product of its digits is 14336, while the sum is 34.

The square root of 21242878 is about 4608.9996745498. Note that the first 3 decimals coincide. The cubic root of 21242878 is about 276.9519655008.

The spelling of 21242878 in words is "twenty-one million, two hundred forty-two thousand, eight hundred seventy-eight".