21517930 has 16 divisors (see below), whose sum is σ = 44265600. Its totient is φ = 7377552.

The previous prime is 21517919. The next prime is 21517957. The reversal of 21517930 is 3971512.

It is a super-2 number, since 2×21517930² = 926042622969800, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 153630 + ... + 153769.

It is an arithmetic number, because the mean of its divisors is an integer number (2766600).

Almost surely, 2^21517930 is an apocalyptic number.

21517930 is an abundant number, since it is smaller than the sum of its proper divisors (22747670).

21517930 is a wasteful number, since it uses less digits than its factorization.

21517930 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 307413.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21517930 is about 4638.7422864393. The cubic root of 21517930 is about 278.1421645763.

It can be divided in two parts, 215 and 17930, that added together give a triangular number (18145 = T₁₉₀).

The spelling of 21517930 in words is "twenty-one million, five hundred seventeen thousand, nine hundred thirty".