21146640 has 160 divisors (see below), whose sum is σ = 71352576. Its totient is φ = 5160960.

The previous prime is 21146633. The next prime is 21146717. The reversal of 21146640 is 4664112.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21146640.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 289644 + ... + 289716.

Almost surely, 2^21146640 is an apocalyptic number.

21146640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21146640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35676288).

21146640 is an abundant number, since it is smaller than the sum of its proper divisors (50205936).

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

21146640 is a wasteful number, since it uses less digits than its factorization.

21146640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177 (or 171 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21146640 is about 4598.5475967962. The cubic root of 21146640 is about 276.5331011234.

The spelling of 21146640 in words is "twenty-one million, one hundred forty-six thousand, six hundred forty".