21216570 has 16 divisors (see below), whose sum is σ = 50919840. Its totient is φ = 5657744.

The previous prime is 21216553. The next prime is 21216607. The reversal of 21216570 is 7561212.

It is a self number, because there is not a number n which added to its sum of digits gives 21216570.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 353580 + ... + 353639.

It is an arithmetic number, because the mean of its divisors is an integer number (3182490).

Almost surely, 2^21216570 is an apocalyptic number.

21216570 is an abundant number, since it is smaller than the sum of its proper divisors (29703270).

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

21216570 is a wasteful number, since it uses less digits than its factorization.

21216570 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 707229.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21216570 is about 4606.1448088396. The cubic root of 21216570 is about 276.8375889373.

Adding to 21216570 its reverse (7561212), we get a palindrome (28777782).

The spelling of 21216570 in words is "twenty-one million, two hundred sixteen thousand, five hundred seventy".