21931970 has 8 divisors (see below), whose sum is σ = 39477564. Its totient is φ = 8772784.

The previous prime is 21931969. The next prime is 21931979. The reversal of 21931970 is 7913912.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21446161 + 485809 = 4631^2 + 697^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21931970² = 962022616161800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21931979) 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 3 ways as a sum of consecutive naturals, for example, 1096589 + ... + 1096608.

Almost surely, 2^21931970 is an apocalyptic number.

21931970 is a deficient number, since it is larger than the sum of its proper divisors (17545594).

21931970 is a wasteful number, since it uses less digits than its factorization.

21931970 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2193204.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21931970 is about 4683.1581224639. The cubic root of 21931970 is about 279.9148125205.

The spelling of 21931970 in words is "twenty-one million, nine hundred thirty-one thousand, nine hundred seventy".