21605974 has 24 divisors (see below), whose sum is σ = 35509320. Its totient is φ = 9854208.

The previous prime is 21605971. The next prime is 21605981. The reversal of 21605974 is 47950612.

It is a super-2 number, since 2×21605974² = 933636224977352, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605971) 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 in 11 ways as a sum of consecutive naturals, for example, 32457 + ... + 33115.

It is an arithmetic number, because the mean of its divisors is an integer number (1479555).

Almost surely, 2^21605974 is an apocalyptic number.

21605974 is a deficient number, since it is larger than the sum of its proper divisors (13903346).

21605974 is a wasteful number, since it uses less digits than its factorization.

21605974 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 784 (or 771 counting only the distinct ones).

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21605974 is about 4648.2226710862. Note that the first 3 decimals coincide. The cubic root of 21605974 is about 278.5210025128.

The spelling of 21605974 in words is "twenty-one million, six hundred five thousand, nine hundred seventy-four".