21530745 has 32 divisors (see below), whose sum is σ = 39177600. Its totient is φ = 11212992.

The previous prime is 21530741. The next prime is 21530749. The reversal of 21530745 is 54703512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21530741) and next prime (21530749).

It is not a de Polignac number, because 21530745 - 2² = 21530741 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21530741) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3951 + ... + 7659.

It is an arithmetic number, because the mean of its divisors is an integer number (1224300).

Almost surely, 2^21530745 is an apocalyptic number.

It is an amenable number.

21530745 is a deficient number, since it is larger than the sum of its proper divisors (17646855).

21530745 is a wasteful number, since it uses less digits than its factorization.

21530745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3766 (or 3760 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 27.

The square root of 21530745 is about 4640.1233819803. The cubic root of 21530745 is about 278.1973694602.

The spelling of 21530745 in words is "twenty-one million, five hundred thirty thousand, seven hundred forty-five".