21511542 has 32 divisors (see below), whose sum is σ = 46932480. Its totient is φ = 6533280.

The previous prime is 21511537. The next prime is 21511547. The reversal of 21511542 is 24511512.

It is an interprime number because it is at equal distance from previous prime (21511537) and next prime (21511547).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21511547) 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 15 ways as a sum of consecutive naturals, for example, 4417 + ... + 7907.

It is an arithmetic number, because the mean of its divisors is an integer number (1466640).

Almost surely, 2^21511542 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21511542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23466240).

21511542 is an abundant number, since it is smaller than the sum of its proper divisors (25420938).

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

21511542 is a wasteful number, since it uses less digits than its factorization.

21511542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3588.

The product of its digits is 400, while the sum is 21.

The square root of 21511542 is about 4638.0536866233. The cubic root of 21511542 is about 278.1146379509.

The spelling of 21511542 in words is "twenty-one million, five hundred eleven thousand, five hundred forty-two".