21019957 has 8 divisors (see below), whose sum is σ = 24076800. Its totient is φ = 17976624.

The previous prime is 21019937. The next prime is 21019961. The reversal of 21019957 is 75991012.

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

It is a cyclic number.

It is not a de Polignac number, because 21019957 - 2¹⁵ = 20987189 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 (21019927) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 219 + ... + 6487.

It is an arithmetic number, because the mean of its divisors is an integer number (3009600).

Almost surely, 2^21019957 is an apocalyptic number.

It is an amenable number.

21019957 is a deficient number, since it is larger than the sum of its proper divisors (3056843).

21019957 is an equidigital number, since it uses as much as digits as its factorization.

21019957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6755.

The product of its (nonzero) digits is 5670, while the sum is 34.

The square root of 21019957 is about 4584.7526650846. The cubic root of 21019957 is about 275.9797865544.

The spelling of 21019957 in words is "twenty-one million, nineteen thousand, nine hundred fifty-seven".