21211861 has 4 divisors (see below), whose sum is σ = 23140224. Its totient is φ = 19283500.

The previous prime is 21211859. The next prime is 21211867. The reversal of 21211861 is 16811212.

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 21211861 - 2¹ = 21211859 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211867) 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 3 ways as a sum of consecutive naturals, for example, 964165 + ... + 964186.

It is an arithmetic number, because the mean of its divisors is an integer number (5785056).

Almost surely, 2^21211861 is an apocalyptic number.

It is an amenable number.

21211861 is a deficient number, since it is larger than the sum of its proper divisors (1928363).

21211861 is a wasteful number, since it uses less digits than its factorization.

21211861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1928362.

The product of its digits is 192, while the sum is 22.

The square root of 21211861 is about 4605.6336154757. The cubic root of 21211861 is about 276.8171061312.

The spelling of 21211861 in words is "twenty-one million, two hundred eleven thousand, eight hundred sixty-one".