21016890 has 48 divisors (see below), whose sum is σ = 54899208. Its totient is φ = 5578368.

The previous prime is 21016883. The next prime is 21016901. The reversal of 21016890 is 9861012.

It can be written as a sum of positive squares in 4 ways, for example, as 20223009 + 793881 = 4497^2 + 891^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25972 + ... + 26768.

Almost surely, 2^21016890 is an apocalyptic number.

21016890 is an abundant number, since it is smaller than the sum of its proper divisors (33882318).

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

21016890 is a wasteful number, since it uses less digits than its factorization.

21016890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1103 (or 1100 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 21016890 is about 4584.4181746433. The cubic root of 21016890 is about 275.9663632606.

The spelling of 21016890 in words is "twenty-one million, sixteen thousand, eight hundred ninety".