21355906 has 32 divisors (see below), whose sum is σ = 38102400. Its totient is φ = 8849280.

The previous prime is 21355903. The next prime is 21355909. The reversal of 21355906 is 60955312.

It is an interprime number because it is at equal distance from previous prime (21355903) and next prime (21355909).

It is not an unprimeable number, because it can be changed into a prime (21355903) 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, 25035 + ... + 25873.

It is an arithmetic number, because the mean of its divisors is an integer number (1190700).

Almost surely, 2^21355906 is an apocalyptic number.

21355906 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21355906 is a deficient number, since it is larger than the sum of its proper divisors (16746494).

21355906 is a wasteful number, since it uses less digits than its factorization.

21355906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 954.

The product of its (nonzero) digits is 8100, while the sum is 31.

The square root of 21355906 is about 4621.2450703247. The cubic root of 21355906 is about 277.4422940908.

The spelling of 21355906 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred six".