215457661 has 8 divisors (see below), whose sum is σ = 219723840. Its totient is φ = 211233408.

The previous prime is 215457653. The next prime is 215457679. The reversal of 215457661 is 166754512.

It is a happy number.

215457661 is a nontrivial binomial coefficient, being equal to C(20759, 2).

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

It is not a de Polignac number, because 215457661 - 2³ = 215457653 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 215457661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215457601) 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, 1 + ... + 20758.

It is an arithmetic number, because the mean of its divisors is an integer number (27465480).

Almost surely, 2^215457661 is an apocalyptic number.

215457661 is the 20758-th triangular number.

215457661 is the 6920-th centered nonagonal number.

It is an amenable number.

215457661 is a deficient number, since it is larger than the sum of its proper divisors (4266179).

215457661 is a wasteful number, since it uses less digits than its factorization.

215457661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20963.

The product of its digits is 50400, while the sum is 37.

The square root of 215457661 is about 14678.4761130030. The cubic root of 215457661 is about 599.4974133880.

The spelling of 215457661 in words is "two hundred fifteen million, four hundred fifty-seven thousand, six hundred sixty-one".