21252261 has 16 divisors (see below), whose sum is σ = 30241728. Its totient is φ = 13228800.

The previous prime is 21252251. The next prime is 21252269. The reversal of 21252261 is 16225212.

21252261 = 336² + 337² + ... + 466².

It is a happy number.

It is not a de Polignac number, because 21252261 - 2¹⁵ = 21219493 is a prime.

It is a super-2 number, since 2×21252261² = 903317195224242, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252269) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5091 + ... + 8271.

It is an arithmetic number, because the mean of its divisors is an integer number (1890108).

Almost surely, 2^21252261 is an apocalyptic number.

It is an amenable number.

21252261 is a deficient number, since it is larger than the sum of its proper divisors (8989467).

21252261 is a wasteful number, since it uses less digits than its factorization.

21252261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3332.

The product of its digits is 480, while the sum is 21.

The square root of 21252261 is about 4610.0174620060. The cubic root of 21252261 is about 276.9927361500.

Adding to 21252261 its reverse (16225212), we get a palindrome (37477473).

The spelling of 21252261 in words is "twenty-one million, two hundred fifty-two thousand, two hundred sixty-one".