21690955 has 32 divisors (see below), whose sum is σ = 31933440. Its totient is φ = 13918080.

The previous prime is 21690943. The next prime is 21690959. The reversal of 21690955 is 55909612.

It is not a de Polignac number, because 21690955 - 2¹⁷ = 21559883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21690959) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 15786 + ... + 17104.

It is an arithmetic number, because the mean of its divisors is an integer number (997920).

Almost surely, 2^21690955 is an apocalyptic number.

21690955 is a deficient number, since it is larger than the sum of its proper divisors (10242485).

21690955 is a wasteful number, since it uses less digits than its factorization.

21690955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1371.

The product of its (nonzero) digits is 24300, while the sum is 37.

The square root of 21690955 is about 4657.3549360125. The cubic root of 21690955 is about 278.8856860517.

The spelling of 21690955 in words is "twenty-one million, six hundred ninety thousand, nine hundred fifty-five".