21421003501 has 8 divisors (see below), whose sum is σ = 21476292344. Its totient is φ = 21365752320.

The previous prime is 21421003477. The next prime is 21421003559. The reversal of 21421003501 is 10530012412.

It can be written as a sum of positive squares in 4 ways, for example, as 4819969476 + 16601034025 = 69426^2 + 128845^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21421003501 - 2⁵ = 21421003469 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 (21421003301) 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, 1391221 + ... + 1406533.

It is an arithmetic number, because the mean of its divisors is an integer number (2684536543).

Almost surely, 2^21421003501 is an apocalyptic number.

21421003501 is the 84501-st hex number.

It is an amenable number.

21421003501 is a deficient number, since it is larger than the sum of its proper divisors (55288843).

21421003501 is a wasteful number, since it uses less digits than its factorization.

21421003501 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18831.

The product of its (nonzero) digits is 240, while the sum is 19.

Adding to 21421003501 its reverse (10530012412), we get a palindrome (31951015913).

The spelling of 21421003501 in words is "twenty-one billion, four hundred twenty-one million, three thousand, five hundred one".