21505470 has 32 divisors (see below), whose sum is σ = 58987008. Its totient is φ = 4915488.

The previous prime is 21505469. The next prime is 21505481. The reversal of 21505470 is 7450512.

It is a self number, because there is not a number n which added to its sum of digits gives 21505470.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 50994 + ... + 51413.

It is an arithmetic number, because the mean of its divisors is an integer number (1843344).

Almost surely, 2^21505470 is an apocalyptic number.

21505470 is an abundant number, since it is smaller than the sum of its proper divisors (37481538).

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

21505470 is a wasteful number, since it uses less digits than its factorization.

21505470 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102424.

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21505470 is about 4637.3990555051. The cubic root of 21505470 is about 278.0884679534.

Adding to 21505470 its reverse (7450512), we get a palindrome (28955982).

The spelling of 21505470 in words is "twenty-one million, five hundred five thousand, four hundred seventy".