21262661 has 4 divisors (see below), whose sum is σ = 24300192. Its totient is φ = 18225132.

The previous prime is 21262643. The next prime is 21262663. The reversal of 21262661 is 16626212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21262661 - 2¹⁸ = 21000517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21262661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21262663) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1518755 + ... + 1518768.

It is an arithmetic number, because the mean of its divisors is an integer number (6075048).

Almost surely, 2^21262661 is an apocalyptic number.

It is an amenable number.

21262661 is a deficient number, since it is larger than the sum of its proper divisors (3037531).

21262661 is an equidigital number, since it uses as much as digits as its factorization.

21262661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3037530.

The product of its digits is 1728, while the sum is 26.

The square root of 21262661 is about 4611.1453024167. The cubic root of 21262661 is about 277.0379118089.

Adding to 21262661 its reverse (16626212), we get a palindrome (37888873).

The spelling of 21262661 in words is "twenty-one million, two hundred sixty-two thousand, six hundred sixty-one".