21506193 has 6 divisors (see below), whose sum is σ = 31064514. Its totient is φ = 14337456.

The previous prime is 21506167. The next prime is 21506201. The reversal of 21506193 is 39160512.

It can be written as a sum of positive squares in only one way, i.e., 15586704 + 5919489 = 3948^2 + 2433^2 .

It is not a de Polignac number, because 21506193 - 2⁹ = 21505681 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21506143) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1194780 + ... + 1194797.

It is an arithmetic number, because the mean of its divisors is an integer number (5177419).

Almost surely, 2^21506193 is an apocalyptic number.

It is an amenable number.

21506193 is a deficient number, since it is larger than the sum of its proper divisors (9558321).

21506193 is a wasteful number, since it uses less digits than its factorization.

21506193 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2389583 (or 2389580 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 27.

The square root of 21506193 is about 4637.4770080293. The cubic root of 21506193 is about 278.0915843034.

The spelling of 21506193 in words is "twenty-one million, five hundred six thousand, one hundred ninety-three".