21215654 has 4 divisors (see below), whose sum is σ = 31823484. Its totient is φ = 10607826.

The previous prime is 21215627. The next prime is 21215657. The reversal of 21215654 is 45651212.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21215657) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5303912 + ... + 5303915.

It is an arithmetic number, because the mean of its divisors is an integer number (7955871).

Almost surely, 2^21215654 is an apocalyptic number.

21215654 is a deficient number, since it is larger than the sum of its proper divisors (10607830).

21215654 is a wasteful number, since it uses less digits than its factorization.

21215654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10607829.

The product of its digits is 2400, while the sum is 26.

The square root of 21215654 is about 4606.0453753735. The cubic root of 21215654 is about 276.8336048361.

Adding to 21215654 its reverse (45651212), we get a palindrome (66866866).

The spelling of 21215654 in words is "twenty-one million, two hundred fifteen thousand, six hundred fifty-four".