21953931 has 4 divisors (see below), whose sum is σ = 29271912. Its totient is φ = 14635952.

The previous prime is 21953923. The next prime is 21953963. The reversal of 21953931 is 13935912.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21953931 - 2³ = 21953923 is a prime.

It is a super-2 number, since 2×21953931² = 963950172705522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21953892 and 21953901.

It is not an unprimeable number, because it can be changed into a prime (21953831) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3658986 + ... + 3658991.

It is an arithmetic number, because the mean of its divisors is an integer number (7317978).

Almost surely, 2^21953931 is an apocalyptic number.

21953931 is a deficient number, since it is larger than the sum of its proper divisors (7317981).

21953931 is an equidigital number, since it uses as much as digits as its factorization.

21953931 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7317980.

The product of its digits is 7290, while the sum is 33.

The square root of 21953931 is about 4685.5022142776. The cubic root of 21953931 is about 280.0082097933.

The spelling of 21953931 in words is "twenty-one million, nine hundred fifty-three thousand, nine hundred thirty-one".