21061530 has 96 divisors (see below), whose sum is σ = 63393408. Its totient is φ = 4752000.

The previous prime is 21061507. The next prime is 21061541. The reversal of 21061530 is 3516012.

21061530 is a `hidden beast` number, since 21 + 0 + 615 + 30 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

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 47 ways as a sum of consecutive naturals, for example, 63465 + ... + 63795.

It is an arithmetic number, because the mean of its divisors is an integer number (660348).

Almost surely, 2^21061530 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21061530, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31696704).

21061530 is an abundant number, since it is smaller than the sum of its proper divisors (42331878).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21061530 is a wasteful number, since it uses less digits than its factorization.

21061530 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 452 (or 449 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21061530 is about 4589.2842579208. The cubic root of 21061530 is about 276.1616098259.

Adding to 21061530 its reverse (3516012), we get a palindrome (24577542).

The spelling of 21061530 in words is "twenty-one million, sixty-one thousand, five hundred thirty".