21381501 has 8 divisors (see below), whose sum is σ = 28634080. Its totient is φ = 14191632.

The previous prime is 21381491. The next prime is 21381527. The reversal of 21381501 is 10518312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21381501 - 2⁵ = 21381469 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14875 + ... + 16248.

It is an arithmetic number, because the mean of its divisors is an integer number (3579260).

Almost surely, 2^21381501 is an apocalyptic number.

It is an amenable number.

21381501 is a deficient number, since it is larger than the sum of its proper divisors (7252579).

21381501 is a wasteful number, since it uses less digits than its factorization.

21381501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31355.

The product of its (nonzero) digits is 240, while the sum is 21.

The square root of 21381501 is about 4624.0135164162. The cubic root of 21381501 is about 277.5530878061.

Adding to 21381501 its reverse (10518312), we get a palindrome (31899813).

The spelling of 21381501 in words is "twenty-one million, three hundred eighty-one thousand, five hundred one".