21621145 has 64 divisors (see below), whose sum is σ = 34997760. Its totient is φ = 12441600.

The previous prime is 21621143. The next prime is 21621179. The reversal of 21621145 is 54112612.

It is not a de Polignac number, because 21621145 - 2¹ = 21621143 is a prime.

It is a super-2 number, since 2×21621145² = 934947822222050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21621143) by changing a digit.

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 63 ways as a sum of consecutive naturals, for example, 354415 + ... + 354475.

It is an arithmetic number, because the mean of its divisors is an integer number (546840).

Almost surely, 2^21621145 is an apocalyptic number.

It is an amenable number.

21621145 is a deficient number, since it is larger than the sum of its proper divisors (13376615).

21621145 is a wasteful number, since it uses less digits than its factorization.

21621145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 146.

The product of its digits is 480, while the sum is 22.

The square root of 21621145 is about 4649.8542987926. The cubic root of 21621145 is about 278.5861766714.

Adding to 21621145 its reverse (54112612), we get a palindrome (75733757).

The spelling of 21621145 in words is "twenty-one million, six hundred twenty-one thousand, one hundred forty-five".