21215156 has 6 divisors (see below), whose sum is σ = 37126530. Its totient is φ = 10607576.

The previous prime is 21215147. The next prime is 21215203. The reversal of 21215156 is 65151212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20702500 + 512656 = 4550^2 + 716^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2651891 + ... + 2651898.

It is an arithmetic number, because the mean of its divisors is an integer number (6187755).

Almost surely, 2^21215156 is an apocalyptic number.

It is an amenable number.

21215156 is a deficient number, since it is larger than the sum of its proper divisors (15911374).

21215156 is a wasteful number, since it uses less digits than its factorization.

21215156 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5303793 (or 5303791 counting only the distinct ones).

The product of its digits is 600, while the sum is 23.

The square root of 21215156 is about 4605.9913156670. The cubic root of 21215156 is about 276.8314387593.

Adding to 21215156 its reverse (65151212), we get a palindrome (86366368).

The spelling of 21215156 in words is "twenty-one million, two hundred fifteen thousand, one hundred fifty-six".