21630540 has 24 divisors (see below), whose sum is σ = 60565680. Its totient is φ = 5768128.

The previous prime is 21630527. The next prime is 21630541. The reversal of 21630540 is 4503612.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21630541) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 180195 + ... + 180314.

It is an arithmetic number, because the mean of its divisors is an integer number (2523570).

Almost surely, 2^21630540 is an apocalyptic number.

21630540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21630540 is an abundant number, since it is smaller than the sum of its proper divisors (38935140).

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

21630540 is a wasteful number, since it uses less digits than its factorization.

21630540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360521 (or 360519 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21630540 is about 4650.8644357797. The cubic root of 21630540 is about 278.6265220234.

The spelling of 21630540 in words is "twenty-one million, six hundred thirty thousand, five hundred forty".