21215151 has 12 divisors (see below), whose sum is σ = 30948840. Its totient is φ = 14002800.

The previous prime is 21215147. The next prime is 21215203. The reversal of 21215151 is 15151212.

It is not a de Polignac number, because 21215151 - 2² = 21215147 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215101) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10761 + ... + 12578.

It is an arithmetic number, because the mean of its divisors is an integer number (2579070).

Almost surely, 2^21215151 is an apocalyptic number.

21215151 is a deficient number, since it is larger than the sum of its proper divisors (9733689).

21215151 is a wasteful number, since it uses less digits than its factorization.

21215151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23446 (or 23443 counting only the distinct ones).

The product of its digits is 100, while the sum is 18.

The square root of 21215151 is about 4605.9907728957. The cubic root of 21215151 is about 276.8314170113.

Adding to 21215151 its reverse (15151212), we get a palindrome (36366363).

The spelling of 21215151 in words is "twenty-one million, two hundred fifteen thousand, one hundred fifty-one".