21491630 has 16 divisors (see below), whose sum is σ = 38765520. Its totient is φ = 8578752.

The previous prime is 21491627. The next prime is 21491633. The reversal of 21491630 is 3619412.

It is an interprime number because it is at equal distance from previous prime (21491627) and next prime (21491633).

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 21491630.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21491633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3506 + ... + 7434.

It is an arithmetic number, because the mean of its divisors is an integer number (2422845).

Almost surely, 2^21491630 is an apocalyptic number.

21491630 is a deficient number, since it is larger than the sum of its proper divisors (17273890).

21491630 is a wasteful number, since it uses less digits than its factorization.

21491630 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4483.

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 21491630 is about 4635.9065995768. The cubic root of 21491630 is about 278.0287998733.

The spelling of 21491630 in words is "twenty-one million, four hundred ninety-one thousand, six hundred thirty".