21520045 has 16 divisors (see below), whose sum is σ = 28228608. Its totient is φ = 15678720.

The previous prime is 21520021. The next prime is 21520061. The reversal of 21520045 is 54002512.

It is not a de Polignac number, because 21520045 - 2⁵ = 21520013 is a prime.

It is a super-2 number, since 2×21520045² = 926224673604050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1449 + ... + 6718.

It is an arithmetic number, because the mean of its divisors is an integer number (1764288).

Almost surely, 2^21520045 is an apocalyptic number.

It is an amenable number.

21520045 is a deficient number, since it is larger than the sum of its proper divisors (6708563).

21520045 is a wasteful number, since it uses less digits than its factorization.

21520045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8220.

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21520045 is about 4638.9702521141. The cubic root of 21520045 is about 278.1512771537.

Adding to 21520045 its reverse (54002512), we get a palindrome (75522557).

The spelling of 21520045 in words is "twenty-one million, five hundred twenty thousand, forty-five".