21138890 has 16 divisors (see below), whose sum is σ = 38102400. Its totient is φ = 8443920.

The previous prime is 21138881. The next prime is 21138911. The reversal of 21138890 is 9883112.

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 7 ways as a sum of consecutive naturals, for example, 13235 + ... + 14745.

It is an arithmetic number, because the mean of its divisors is an integer number (2381400).

Almost surely, 2^21138890 is an apocalyptic number.

21138890 is a deficient number, since it is larger than the sum of its proper divisors (16963510).

21138890 is a wasteful number, since it uses less digits than its factorization.

21138890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2917.

The product of its (nonzero) digits is 3456, while the sum is 32.

The square root of 21138890 is about 4597.7048622111. The cubic root of 21138890 is about 276.4993149302.

The spelling of 21138890 in words is "twenty-one million, one hundred thirty-eight thousand, eight hundred ninety".