21215191 has 16 divisors (see below), whose sum is σ = 23296000. Its totient is φ = 19245600.

The previous prime is 21215147. The next prime is 21215203. The reversal of 21215191 is 19151212.

It is a cyclic number.

It is not a de Polignac number, because 21215191 - 2⁷ = 21215063 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 (21215101) 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, 106510 + ... + 106708.

It is an arithmetic number, because the mean of its divisors is an integer number (1456000).

Almost surely, 2^21215191 is an apocalyptic number.

21215191 is a deficient number, since it is larger than the sum of its proper divisors (2080809).

21215191 is a wasteful number, since it uses less digits than its factorization.

21215191 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 430.

The product of its digits is 180, while the sum is 22.

The square root of 21215191 is about 4605.9951150647. The cubic root of 21215191 is about 276.8315909947.

The spelling of 21215191 in words is "twenty-one million, two hundred fifteen thousand, one hundred ninety-one".