21700261 has 12 divisors (see below), whose sum is σ = 25110400. Its totient is φ = 18687240.

The previous prime is 21700253. The next prime is 21700291. The reversal of 21700261 is 16200712.

It is not a de Polignac number, because 21700261 - 2³ = 21700253 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21700291) 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 11 ways as a sum of consecutive naturals, for example, 2421 + ... + 7018.

Almost surely, 2^21700261 is an apocalyptic number.

It is an amenable number.

21700261 is a deficient number, since it is larger than the sum of its proper divisors (3410139).

21700261 is a wasteful number, since it uses less digits than its factorization.

21700261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9480 (or 9469 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 21700261 is about 4658.3538938127. The cubic root of 21700261 is about 278.9255634895.

Adding to 21700261 its reverse (16200712), we get a palindrome (37900973).

The spelling of 21700261 in words is "twenty-one million, seven hundred thousand, two hundred sixty-one".