21456890 has 128 divisors (see below), whose sum is σ = 53706240. Its totient is φ = 5971968.

The previous prime is 21456889. The next prime is 21456893. The reversal of 21456890 is 9865412.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21456890.

It is not an unprimeable number, because it can be changed into a prime (21456893) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 293894 + ... + 293966.

It is an arithmetic number, because the mean of its divisors is an integer number (419580).

Almost surely, 2^21456890 is an apocalyptic number.

21456890 is an abundant number, since it is smaller than the sum of its proper divisors (32249350).

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

21456890 is a wasteful number, since it uses less digits than its factorization.

21456890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21456890 is about 4632.1582442745. The cubic root of 21456890 is about 277.8789131586.

The spelling of 21456890 in words is "twenty-one million, four hundred fifty-six thousand, eight hundred ninety".