21500649 has 6 divisors (see below), whose sum is σ = 31056506. Its totient is φ = 14333760.

The previous prime is 21500641. The next prime is 21500651. The reversal of 21500649 is 94600512.

21500649 is a `hidden beast` number, since 2 + 15 + 0 + 0 + 649 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21483225 + 17424 = 4635^2 + 132^2 .

It is not a de Polignac number, because 21500649 - 2³ = 21500641 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21500641) 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, 1194472 + ... + 1194489.

Almost surely, 2^21500649 is an apocalyptic number.

It is an amenable number.

21500649 is a deficient number, since it is larger than the sum of its proper divisors (9555857).

21500649 is a wasteful number, since it uses less digits than its factorization.

21500649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2388967 (or 2388964 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21500649 is about 4636.8792306895. The cubic root of 21500649 is about 278.0676861911.

The spelling of 21500649 in words is "twenty-one million, five hundred thousand, six hundred forty-nine".