21621867 has 16 divisors (see below), whose sum is σ = 30576000. Its totient is φ = 13552704.

The previous prime is 21621851. The next prime is 21621871. The reversal of 21621867 is 76812612.

It is not a de Polignac number, because 21621867 - 2⁴ = 21621851 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21621767) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6559 + ... + 9287.

It is an arithmetic number, because the mean of its divisors is an integer number (1911000).

Almost surely, 2^21621867 is an apocalyptic number.

21621867 is a deficient number, since it is larger than the sum of its proper divisors (8954133).

21621867 is a wasteful number, since it uses less digits than its factorization.

21621867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2890.

The product of its digits is 8064, while the sum is 33.

The square root of 21621867 is about 4649.9319349857. The cubic root of 21621867 is about 278.5892776015.

The spelling of 21621867 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred sixty-seven".