21961997 has 8 divisors (see below), whose sum is σ = 22425312. Its totient is φ = 21502800.

The previous prime is 21961993. The next prime is 21962021. The reversal of 21961997 is 79916912.

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

It is not a de Polignac number, because 21961997 - 2² = 21961993 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21961991) 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 7 ways as a sum of consecutive naturals, for example, 11222 + ... + 13032.

It is an arithmetic number, because the mean of its divisors is an integer number (2803164).

Almost surely, 2^21961997 is an apocalyptic number.

It is an amenable number.

21961997 is a deficient number, since it is larger than the sum of its proper divisors (463315).

21961997 is a wasteful number, since it uses less digits than its factorization.

21961997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2059.

The product of its digits is 61236, while the sum is 44.

The square root of 21961997 is about 4686.3628754078. The cubic root of 21961997 is about 280.0424978011.

The spelling of 21961997 in words is "twenty-one million, nine hundred sixty-one thousand, nine hundred ninety-seven".