21520365 has 8 divisors (see below), whose sum is σ = 34432608. Its totient is φ = 11477520.

The previous prime is 21520363. The next prime is 21520391. The reversal of 21520365 is 56302512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21520365 - 2¹ = 21520363 is a prime.

It is a super-2 number, since 2×21520365² = 926252219466450, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520361) 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, 717331 + ... + 717360.

It is an arithmetic number, because the mean of its divisors is an integer number (4304076).

Almost surely, 2^21520365 is an apocalyptic number.

It is an amenable number.

21520365 is a deficient number, since it is larger than the sum of its proper divisors (12912243).

21520365 is a wasteful number, since it uses less digits than its factorization.

21520365 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1434699.

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21520365 is about 4639.0047423990. The cubic root of 21520365 is about 278.1526558368.

Adding to 21520365 its reverse (56302512), we get a palindrome (77822877).

The spelling of 21520365 in words is "twenty-one million, five hundred twenty thousand, three hundred sixty-five".