21706530 has 16 divisors (see below), whose sum is σ = 52095744. Its totient is φ = 5788400.

The previous prime is 21706523. The next prime is 21706537. The reversal of 21706530 is 3560712.

It is an interprime number because it is at equal distance from previous prime (21706523) and next prime (21706537).

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 21706530.

It is not an unprimeable number, because it can be changed into a prime (21706537) 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, 361746 + ... + 361805.

It is an arithmetic number, because the mean of its divisors is an integer number (3255984).

Almost surely, 2^21706530 is an apocalyptic number.

21706530 is an abundant number, since it is smaller than the sum of its proper divisors (30389214).

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

21706530 is a wasteful number, since it uses less digits than its factorization.

21706530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 723561.

The product of its (nonzero) digits is 1260, while the sum is 24.

The square root of 21706530 is about 4659.0267223960. The cubic root of 21706530 is about 278.9524205552.

The spelling of 21706530 in words is "twenty-one million, seven hundred six thousand, five hundred thirty".