21501213 has 8 divisors (see below), whose sum is σ = 28795488. Its totient is φ = 14270544.

The previous prime is 21501211. The next prime is 21501229. The reversal of 21501213 is 31210512.

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

It is not a de Polignac number, because 21501213 - 2¹ = 21501211 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21501192 and 21501201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21501211) 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, 15106 + ... + 16467.

It is an arithmetic number, because the mean of its divisors is an integer number (3599436).

Almost surely, 2^21501213 is an apocalyptic number.

It is an amenable number.

21501213 is a deficient number, since it is larger than the sum of its proper divisors (7294275).

21501213 is a wasteful number, since it uses less digits than its factorization.

21501213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31803.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21501213 is about 4636.9400470569. The cubic root of 21501213 is about 278.0701175721.

Adding to 21501213 its reverse (31210512), we get a palindrome (52711725).

The spelling of 21501213 in words is "twenty-one million, five hundred one thousand, two hundred thirteen".