21552405 has 64 divisors (see below), whose sum is σ = 41472000. Its totient is φ = 9549120.

The previous prime is 21552383. The next prime is 21552437. The reversal of 21552405 is 50425512.

It is a happy number.

It is not a de Polignac number, because 21552405 - 2⁵ = 21552373 is a prime.

It is a super-2 number, since 2×21552405² = 929012322568050, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 303520 + ... + 303590.

It is an arithmetic number, because the mean of its divisors is an integer number (648000).

Almost surely, 2^21552405 is an apocalyptic number.

It is an amenable number.

21552405 is a deficient number, since it is larger than the sum of its proper divisors (19919595).

21552405 is an equidigital number, since it uses as much as digits as its factorization.

21552405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159 (or 145 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 24.

The square root of 21552405 is about 4642.4567849362. The cubic root of 21552405 is about 278.2906273496.

Adding to 21552405 its reverse (50425512), we get a palindrome (71977917).

It can be divided in two parts, 2155 and 2405, that added together give a triangular number (4560 = T₉₅).

The spelling of 21552405 in words is "twenty-one million, five hundred fifty-two thousand, four hundred five".