21542636 has 6 divisors (see below), whose sum is σ = 37699620. Its totient is φ = 10771316.

The previous prime is 21542623. The next prime is 21542639. The reversal of 21542636 is 63624512.

It is a junction number, because it is equal to n+sod(n) for n = 21542599 and 21542608.

It is not an unprimeable number, because it can be changed into a prime (21542639) 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, 2692826 + ... + 2692833.

It is an arithmetic number, because the mean of its divisors is an integer number (6283270).

Almost surely, 2^21542636 is an apocalyptic number.

It is an amenable number.

21542636 is a deficient number, since it is larger than the sum of its proper divisors (16156984).

21542636 is a wasteful number, since it uses less digits than its factorization.

21542636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5385663 (or 5385661 counting only the distinct ones).

The product of its digits is 8640, while the sum is 29.

The square root of 21542636 is about 4641.4045288038. The cubic root of 21542636 is about 278.2485743166.

The spelling of 21542636 in words is "twenty-one million, five hundred forty-two thousand, six hundred thirty-six".