21151540 has 12 divisors (see below), whose sum is σ = 44418276. Its totient is φ = 8460608.

The previous prime is 21151489. The next prime is 21151561. The reversal of 21151540 is 4515112.

It can be written as a sum of positive squares in 2 ways, for example, as 9400356 + 11751184 = 3066^2 + 3428^2 .

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 3 ways as a sum of consecutive naturals, for example, 528769 + ... + 528808.

It is an arithmetic number, because the mean of its divisors is an integer number (3701523).

Almost surely, 2^21151540 is an apocalyptic number.

21151540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21151540 is an abundant number, since it is smaller than the sum of its proper divisors (23266736).

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

21151540 is a wasteful number, since it uses less digits than its factorization.

21151540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1057586 (or 1057584 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 19.

The square root of 21151540 is about 4599.0803428512. The cubic root of 21151540 is about 276.5544584573.

Adding to 21151540 its reverse (4515112), we get a palindrome (25666652).

It can be divided in two parts, 2115 and 1540, that added together give a triangular number (3655 = T₈₅).

The spelling of 21151540 in words is "twenty-one million, one hundred fifty-one thousand, five hundred forty".