21001261503 has 8 divisors (see below), whose sum is σ = 28019557888. Its totient is φ = 13991903064.

The previous prime is 21001261481. The next prime is 21001261513. The reversal of 21001261503 is 30516210012.

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

It is not a de Polignac number, because 21001261503 - 2⁵ = 21001261471 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 21001261503.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001261513) 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, 2229001 + ... + 2238402.

It is an arithmetic number, because the mean of its divisors is an integer number (3502444736).

Almost surely, 2^21001261503 is an apocalyptic number.

21001261503 is a deficient number, since it is larger than the sum of its proper divisors (7018296385).

21001261503 is a wasteful number, since it uses less digits than its factorization.

21001261503 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4468973.

The product of its (nonzero) digits is 360, while the sum is 21.

Adding to 21001261503 its reverse (30516210012), we get a palindrome (51517471515).

The spelling of 21001261503 in words is "twenty-one billion, one million, two hundred sixty-one thousand, five hundred three".