21870890 has 16 divisors (see below), whose sum is σ = 39536640. Its totient is φ = 8710800.

The previous prime is 21870883. The next prime is 21870931. The reversal of 21870890 is 9807812.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21870890.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 2186 + ... + 6965.

It is an arithmetic number, because the mean of its divisors is an integer number (2471040).

Almost surely, 2^21870890 is an apocalyptic number.

21870890 is a deficient number, since it is larger than the sum of its proper divisors (17665750).

21870890 is a wasteful number, since it uses less digits than its factorization.

21870890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9397.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 21870890 is about 4676.6323353456. The cubic root of 21870890 is about 279.6547189507.

It can be divided in two parts, 218 and 70890, that multiplied together give a triangular number (15454020 = T₅₅₅₉).

The spelling of 21870890 in words is "twenty-one million, eight hundred seventy thousand, eight hundred ninety".