21157910 has 8 divisors (see below), whose sum is σ = 38084256. Its totient is φ = 8463160.

The previous prime is 21157901. The next prime is 21157919. The reversal of 21157910 is 1975112.

It is an interprime number because it is at equal distance from previous prime (21157901) and next prime (21157919).

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

It is a self number, because there is not a number n which added to its sum of digits gives 21157910.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157919) 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, 1057886 + ... + 1057905.

It is an arithmetic number, because the mean of its divisors is an integer number (4760532).

Almost surely, 2^21157910 is an apocalyptic number.

21157910 is a deficient number, since it is larger than the sum of its proper divisors (16926346).

21157910 is a wasteful number, since it uses less digits than its factorization.

21157910 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2115798.

The product of its (nonzero) digits is 630, while the sum is 26.

The square root of 21157910 is about 4599.7728204771. The cubic root of 21157910 is about 276.5822180607.

The spelling of 21157910 in words is "twenty-one million, one hundred fifty-seven thousand, nine hundred ten".