21152501 has 4 divisors (see below), whose sum is σ = 21245100. Its totient is φ = 21059904.

The previous prime is 21152477. The next prime is 21152507. The reversal of 21152501 is 10525112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16851025 + 4301476 = 4105^2 + 2074^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21152501 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21152501.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21152507) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45956 + ... + 46413.

It is an arithmetic number, because the mean of its divisors is an integer number (5311275).

Almost surely, 2^21152501 is an apocalyptic number.

It is an amenable number.

21152501 is a deficient number, since it is larger than the sum of its proper divisors (92599).

21152501 is an equidigital number, since it uses as much as digits as its factorization.

21152501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 92598.

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21152501 is about 4599.1848190739. The cubic root of 21152501 is about 276.5586467230.

Adding to 21152501 its reverse (10525112), we get a palindrome (31677613).

The spelling of 21152501 in words is "twenty-one million, one hundred fifty-two thousand, five hundred one".